Chams: per-colour alpha and a softer viewmodel additive base

- Colour picker gains an optional alpha bar (checkerboard preview, #RRGGBBAA
  readout); add_color_alpha is used for the chams colours. Chams colours are
  now r,g,b,a and chams_apply sets $alpha plus MATERIAL_VAR_TRANSLUCENT when
  alpha < 255. Config stores vis_a / inv_a / vm a.
- The additive viewmodel base is now a faint translucent tint (alpha/8)
  instead of an opaque fill, so additive/Fullbright stay see-through and the
  viewmodel no longer becomes a solid blob. Fullbright whitening reduced to
  25% so blue stays blue instead of turning lavender.

5 files changed, 178 insertions, 66 deletions

diff --git a/CONTEXT.md b/CONTEXT.md
index c75e36c..1bb0a6a 100644
--- a/CONTEXT.md
+++ b/CONTEXT.md
@@ -290,11 +290,16 @@ vocabulary / decisions.
   viewmodel entities (class contains `viewmodel` or model path `.../v_...`)
   are a fourth group.
 - Each relationship has independent **visible** and **through-wall** settings:
-  on/off, style, and colour. The viewmodel has on/off, style and colour only.
-  The through-wall pass uses `MATERIAL_VAR_IGNOREZ` (1 << 15) through
-  `IMaterial::SetMaterialVarFlag` (slot 29); colours use `$color`/`$color2`
-  (IMaterialVar slot 11, SetVecValue 3-float slot 11) and `ColorModulate`
-  (slot 28). Shared materials are restored after each draw.
+  on/off, style, colour and alpha. The viewmodel has on/off, style, colour and
+  alpha only. The through-wall pass uses `MATERIAL_VAR_IGNOREZ` (1 << 15)
+  through `IMaterial::SetMaterialVarFlag` (slot 29); colours use
+  `$color`/`$color2` (IMaterialVar slot 11, SetVecValue 3-float slot 11) and
+  `ColorModulate` (slot 28). Alpha uses `$alpha` (IMaterialVar slot 3,
+  SetFloatValue) and `MATERIAL_VAR_TRANSLUCENT` (1 << 21) when alpha < 255.
+  Shared materials are restored after each draw.
+- The GUI colour picker (`add_color_alpha`) has an alpha bar, checkerboard
+  preview and `#RRGGBBAA` readout; plain `add_color` keeps the old opaque
+  three-component behaviour. Chams colours are four ints (r, g, b, a).
 - Styles are built from `debug/debugtranslucentsinglecolor` (UnlitGeneric,
   `$color`) and material flags:
   0 Flat (solid + FLAT), 1 Wireframe (`debug/debugwireframe`), 2 Additive
@@ -310,12 +315,13 @@ vocabulary / decisions.
 - Viewmodels are collated by the engine as `RENDER_GROUP_VIEW_MODEL_OPAQUE`,
   so an additive forced material can wash out against a bright sky or wall
   (and the engine may not treat the draw as translucent). Additive styles on
-  the viewmodel therefore draw a dim opaque solid base first, then the
-  additive pass; the first-person model never disappears.
+  the viewmodel therefore draw a faint translucent base (alpha/8) first, then
+  the additive pass, so the model keeps a silhouette on bright backgrounds
+  without becoming an opaque blob.
 - Feature is off by default. Config sections: `[chams]` (active/bind),
-  `[chams_hostile|neutral|friendly]` (`vis`, `vis_mat`, `vis_r/g/b`, `inv`,
-  `inv_mat`, `inv_r/g/b`) and `[chams_vm]` (`on`, `mat`, `r/g/b`). The GUI has
-  a Hostile/Neutral/Friendly section each, plus Viewmodel.
+  `[chams_hostile|neutral|friendly]` (`vis`, `vis_mat`, `vis_r/g/b/a`, `inv`,
+  `inv_mat`, `inv_r/g/b/a`) and `[chams_vm]` (`on`, `mat`, `r/g/b/a`). The GUI
+  has a Hostile/Neutral/Friendly section each, plus Viewmodel.
 - This is a material override, not stencil outlines.
 
 ## Bones / ESP
diff --git a/src/gui.cpp b/src/gui.cpp
index 3cbb40a..89888da 100644
--- a/src/gui.cpp
+++ b/src/gui.cpp
@@ -195,7 +195,8 @@ struct Ctrl {
   const char *desc;
   bool *bval; // CK_TOGGLE
   int *ival;  // CK_SLIDER
-  int *rgb;   // CK_COLOR: three ints, 0..255
+  int *rgb;   // CK_COLOR: three or four ints, 0..255 (see has_alpha)
+  bool has_alpha; // CK_COLOR: rgb[3] is an editable alpha channel
   const char *const *opts; // CK_DROPDOWN
   int nopts;               // CK_DROPDOWN
   int min, max;
@@ -256,6 +257,7 @@ static void add_ctrl(int card, int kind, const char *label, const char *desc,
   c.action = action;
   c.zero_unlimited = false;
   c.rgb = nullptr;
+  c.has_alpha = false;
   c.opts = nullptr;
   c.nopts = 0;
   c.hue = 0.0f;
@@ -287,6 +289,14 @@ static void add_color(int card, const char *label, const char *desc,
   add_ctrl(card, CK_COLOR, label, desc, 0, 255, nullptr, nullptr, ACT_NONE);
   g_ctrls[i].rgb = rgb;
 }
+// Same picker, plus an editable alpha bar; rgb must hold four ints.
+static void add_color_alpha(int card, const char *label, const char *desc,
+                            int *rgba) {
+  int i = g_nctrl;
+  add_ctrl(card, CK_COLOR, label, desc, 0, 255, nullptr, nullptr, ACT_NONE);
+  g_ctrls[i].rgb = rgba;
+  g_ctrls[i].has_alpha = true;
+}
 static void add_dropdown(int card, const char *label, const char *desc,
                          const char *const *opts, int nopts, int *value) {
   int i = g_nctrl;
@@ -456,15 +466,15 @@ static void build_cards() {
                &g.vis_on);
     add_dropdown(chams, "Visible material", "Material for the visible pass.",
                  chams_mat_names, 7, &g.vis_mat);
-    add_color(chams, "Visible colour", "Colour for the visible pass.",
-              g.vis_rgb);
+    add_color_alpha(chams, "Visible colour", "Colour and alpha for the visible pass.",
+                    g.vis_rgb);
     add_toggle(chams, "Through walls", "Draw a pass with the depth test off.",
                &g.inv_on);
     add_dropdown(chams, "Invisible material",
                  "Material for the through-wall pass.", chams_mat_names, 7,
                  &g.inv_mat);
-    add_color(chams, "Invisible colour",
-              "Colour for the through-wall pass.", g.inv_rgb);
+    add_color_alpha(chams, "Invisible colour",
+                    "Colour and alpha for the through-wall pass.", g.inv_rgb);
   };
   add_chams_group("Hostile", g_chams_hostile);
   add_chams_group("Neutral", g_chams_neutral);
@@ -475,8 +485,8 @@ static void build_cards() {
              &g_chams_viewmodel);
   add_dropdown(chams, "Viewmodel material", "Material for the viewmodel.",
                chams_mat_names, 7, &g_chams_vm_mat);
-  add_color(chams, "Viewmodel colour", "Colour for the viewmodel.",
-            g_chams_vm_rgb);
+  add_color_alpha(chams, "Viewmodel colour", "Colour and alpha for the viewmodel.",
+                  g_chams_vm_rgb);
   int view = add_card(2, nullptr, "Camera / display",
                       "Camera FOV, viewmodel FOV and HDR brightness.", true);
   add_slider(view, "Camera FOV",
@@ -970,7 +980,7 @@ static int button_w(const char *label) {
 
 static int label_row_h(const Ctrl &c);
 static bool picker_open_for(const Ctrl &c);
-static int picker_panel_h();
+static int picker_panel_h(bool with_alpha);
 static bool card_in_category(int i);
 static Rect card_rect(int index, int y);
 static int card_h(const Card &c);
@@ -978,7 +988,7 @@ static int card_h(const Card &c);
 static int row_h(const Ctrl &c) {
   int h = label_row_h(c);
   if (picker_open_for(c))
-    h += picker_panel_h();
+    h += picker_panel_h(c.has_alpha);
   return h;
 }
 
@@ -989,6 +999,7 @@ static int row_h(const Ctrl &c) {
 static constexpr int PICKER_SV_W = 180;
 static constexpr int PICKER_SV_H = 110;
 static constexpr int PICKER_HUE_H = 12;
+static constexpr int PICKER_ALPHA_H = 12;
 static constexpr int PICKER_GAP = 8;
 
 static bool picker_open_for(const Ctrl &c) {
@@ -996,9 +1007,11 @@ static bool picker_open_for(const Ctrl &c) {
          &c == &g_ctrls[g_picker_ctrl];
 }
 
-static int picker_panel_h() {
-  return S((float)(PICKER_GAP + PICKER_SV_H + PICKER_GAP + PICKER_HUE_H +
-                   PICKER_GAP));
+static int picker_panel_h(bool with_alpha) {
+  int h = PICKER_GAP + PICKER_SV_H + PICKER_GAP + PICKER_HUE_H + PICKER_GAP;
+  if (with_alpha)
+    h += PICKER_ALPHA_H + PICKER_GAP;
+  return S((float)h);
 }
 
 static int label_row_h(const Ctrl &c) {
@@ -1069,16 +1082,17 @@ static void rgb_to_hsv(int r, int g, int b, float &h, float &s, float &v) {
 }
 
 struct PickerRects {
-  Rect panel, sv, hue, preview;
+  Rect panel, sv, hue, alpha, preview;
 };
 
-static PickerRects picker_rects(const Rect &cr, int row_y, int base_h) {
+static PickerRects picker_rects(const Rect &cr, int row_y, int base_h,
+                                bool with_alpha) {
   PickerRects p{};
   int px = cr.x + S(16.0f);
   int py = row_y + base_h;
   int pw = card_content_w() - S(32.0f);
   if (pw > S(340.0f)) pw = S(340.0f);
-  p.panel = Rect{px, py, pw, picker_panel_h()};
+  p.panel = Rect{px, py, pw, picker_panel_h(with_alpha)};
   int preview_w = S(84.0f);
   int svw = S((float)PICKER_SV_W);
   if (svw + preview_w + S(16.0f) > pw)
@@ -1089,6 +1103,8 @@ static PickerRects picker_rects(const Rect &cr, int row_y, int base_h) {
               S((float)PICKER_SV_H)};
   p.hue = Rect{p.sv.x, p.sv.y + p.sv.h + S(PICKER_GAP), svw,
                S((float)PICKER_HUE_H)};
+  p.alpha = Rect{p.hue.x, p.hue.y + p.hue.h + S(PICKER_GAP), svw,
+                 S((float)PICKER_ALPHA_H)};
   p.preview = Rect{p.sv.x + p.sv.w + S(12.0f), p.sv.y, preview_w, S(52.0f)};
   return p;
 }
@@ -1175,7 +1191,7 @@ static bool picker_rects_for(int ctrl_index, PickerRects &out) {
   if (!control_rect(ctrl_index, card, row))
     return false;
   Ctrl &ct = g_ctrls[ctrl_index];
-  out = picker_rects(card, row.y, label_row_h(ct));
+  out = picker_rects(card, row.y, label_row_h(ct), ct.has_alpha);
   return true;
 }
 
@@ -1191,18 +1207,47 @@ static void picker_apply(Ctrl &ct, const PickerRects &p) {
     if (v > 1.0f) v = 1.0f;
     ct.sat = s;
     ct.val = v;
+    hsv_to_rgb(ct.hue, ct.sat, ct.val, ct.rgb[0], ct.rgb[1], ct.rgb[2]);
   } else if (g_picker_drag == 2) {
     float h = 360.0f * (float)(g_mouse_x - p.hue.x) / (float)p.hue.w;
     if (h < 0.0f) h = 0.0f;
     if (h >= 360.0f) h = 359.9f;
     ct.hue = h;
+    hsv_to_rgb(ct.hue, ct.sat, ct.val, ct.rgb[0], ct.rgb[1], ct.rgb[2]);
+  } else if (g_picker_drag == 3 && ct.has_alpha) {
+    if (p.alpha.w <= 0)
+      return;
+    int a = (int)(255.0f * (float)(g_mouse_x - p.alpha.x) /
+                      (float)p.alpha.w +
+                  0.5f);
+    if (a < 0) a = 0;
+    if (a > 255) a = 255;
+    ct.rgb[3] = a;
+  }
+}
+
+static void draw_checker(const Rect &r, const Rect *clip) {
+  int sq = S(6.0f);
+  if (sq < 4)
+    sq = 4;
+  for (int yy = 0; yy < r.h; yy += sq) {
+    for (int xx = 0; xx < r.w; xx += sq) {
+      int w = sq < r.w - xx ? sq : r.w - xx;
+      int h = sq < r.h - yy ? sq : r.h - yy;
+      bool odd = ((xx / sq) + (yy / sq)) & 1;
+      fill(Rect{r.x + xx, r.y + yy, w, h},
+           odd ? Col{62, 66, 74, 255} : Col{38, 41, 47, 255}, clip);
+    }
   }
-  hsv_to_rgb(ct.hue, ct.sat, ct.val, ct.rgb[0], ct.rgb[1], ct.rgb[2]);
 }
 
 static void draw_picker(const Rect &clip, const Rect &cr, const Ctrl &ct,
                         int row_y) {
-  PickerRects p = picker_rects(cr, row_y, label_row_h(ct));
+  PickerRects p = picker_rects(cr, row_y, label_row_h(ct), ct.has_alpha);
+  int pr = ct.rgb ? ct.rgb[0] : 255;
+  int pg = ct.rgb ? ct.rgb[1] : 255;
+  int pb = ct.rgb ? ct.rgb[2] : 255;
+  int pa = (ct.has_alpha && ct.rgb) ? ct.rgb[3] : 255;
   fill(p.panel, Col{20, 23, 29, 250}, &clip);
   outline(p.panel, C_BORDER, &clip);
 
@@ -1236,6 +1281,23 @@ static void draw_picker(const Rect &clip, const Rect &cr, const Ctrl &ct,
   }
   outline(p.hue, Col{0, 0, 0, 255}, &clip);
 
+  // Alpha bar: checkerboard behind a transparent->opaque colour gradient.
+  if (ct.has_alpha) {
+    draw_checker(p.alpha, &clip);
+    int ax = S(4.0f);
+    if (ax < 2) ax = 2;
+    for (int xx = 0; xx < p.alpha.w; xx += ax) {
+      int a = p.alpha.w > 1 ? 255 * xx / (p.alpha.w - 1) : 255;
+      int rw = ax < p.alpha.w - xx ? ax : p.alpha.w - xx;
+      fill(Rect{p.alpha.x + xx, p.alpha.y, rw, p.alpha.h},
+           Col{pr, pg, pb, a}, &clip);
+    }
+    outline(p.alpha, Col{0, 0, 0, 255}, &clip);
+    int amx = p.alpha.x + (int)((float)pa / 255.0f * (float)p.alpha.w);
+    line(amx, p.alpha.y - S(2.0f), amx, p.alpha.y + p.alpha.h + S(2.0f),
+         Col{255, 255, 255, 255});
+  }
+
   // Selection markers.
   int mx = p.sv.x + (int)(ct.sat * (float)p.sv.w);
   int my = p.sv.y + (int)((1.0f - ct.val) * (float)p.sv.h);
@@ -1249,17 +1311,21 @@ static void draw_picker(const Rect &clip, const Rect &cr, const Ctrl &ct,
        Col{255, 255, 255, 255});
 
   // Preview swatch and hex value.
-  int pr = ct.rgb ? ct.rgb[0] : 255;
-  int pg = ct.rgb ? ct.rgb[1] : 255;
-  int pb = ct.rgb ? ct.rgb[2] : 255;
-  fill(p.preview, Col{pr, pg, pb, 255}, &clip);
+  draw_checker(p.preview, &clip);
+  fill(p.preview, Col{pr, pg, pb, pa}, &clip);
   outline(p.preview, C_BORDER, &clip);
   char hex[16];
-  snprintf(hex, sizeof(hex), "#%02X%02X%02X", pr, pg, pb);
+  if (ct.has_alpha)
+    snprintf(hex, sizeof(hex), "#%02X%02X%02X%02X", pr, pg, pb, pa);
+  else
+    snprintf(hex, sizeof(hex), "#%02X%02X%02X", pr, pg, pb);
   text_in(clip, p.preview.x, p.preview.y + p.preview.h + S(8.0f), hex,
           g_font_body, g_body_h, p.preview.w, C_TEXT);
   char rgb[48];
-  snprintf(rgb, sizeof(rgb), "%d %d %d", pr, pg, pb);
+  if (ct.has_alpha)
+    snprintf(rgb, sizeof(rgb), "%d %d %d %d", pr, pg, pb, pa);
+  else
+    snprintf(rgb, sizeof(rgb), "%d %d %d", pr, pg, pb);
   text_in(clip, p.preview.x, p.preview.y + p.preview.h + S(8.0f) + g_body_h,
           rgb, g_font_body, g_body_h, p.preview.w, C_DIM);
 }
@@ -1581,7 +1647,7 @@ static void handle_mouse_click() {
           int base = label_row_h(ct);
           bool is_open = (g_picker_ctrl == idx);
           if (is_open) {
-            PickerRects p = picker_rects(cr, by, base);
+            PickerRects p = picker_rects(cr, by, base, ct.has_alpha);
             if (p.sv.has(mx, my)) {
               g_picker_drag = 1;
               picker_apply(g_ctrls[idx], p);
@@ -1592,6 +1658,11 @@ static void handle_mouse_click() {
               picker_apply(g_ctrls[idx], p);
               return;
             }
+            if (ct.has_alpha && p.alpha.has(mx, my)) {
+              g_picker_drag = 3;
+              picker_apply(g_ctrls[idx], p);
+              return;
+            }
           }
           Rect sw{cr.x + cr.w - S(96.0f), by + (base - S(20.0f)) / 2,
                   S(72.0f), S(20.0f)};
@@ -2015,9 +2086,12 @@ static void draw_card(const Rect &clip, int index, int y) {
         int pr = ct.rgb ? ct.rgb[0] : 255;
         int pg = ct.rgb ? ct.rgb[1] : 255;
         int pb = ct.rgb ? ct.rgb[2] : 255;
+        int pa = (ct.has_alpha && ct.rgb) ? ct.rgb[3] : 255;
         Rect sw{cr.x + cr.w - S(96.0f),
                 by + (base_h - S(20.0f)) / 2, S(72.0f), S(20.0f)};
-        fill(sw, Col{pr, pg, pb, 255}, &clip);
+        if (pa < 255)
+          draw_checker(sw, &clip);
+        fill(sw, Col{pr, pg, pb, pa}, &clip);
         outline(sw, picker_open_for(ct) ? C_ACCENT : C_BORDER, &clip);
         if (picker_open_for(ct))
           draw_picker(clip, cr, ct, by);
diff --git a/src/hl2h.h b/src/hl2h.h
index 4c9012f..f7274f1 100644
--- a/src/hl2h.h
+++ b/src/hl2h.h
@@ -236,15 +236,16 @@ extern bool g_proj_fuse, g_proj_radius;
 struct ChamsGroup {
   bool vis_on;
   int vis_mat;
-  int vis_rgb[3];
+  int vis_rgb[4]; // r, g, b, a (0..255)
   bool inv_on;
   int inv_mat;
-  int inv_rgb[3];
+  int inv_rgb[4];
 };
 extern ChamsGroup g_chams_hostile, g_chams_neutral, g_chams_friendly;
 extern bool g_chams_viewmodel;
 extern int g_chams_vm_mat;
-extern int g_chams_vm_rgb[3];extern bool g_tint_world_on, g_tint_sky_on, g_tint_prop_on;
+extern int g_chams_vm_rgb[4];
+extern bool g_tint_world_on, g_tint_sky_on, g_tint_prop_on;
 extern int g_tint_world_rgb[3], g_tint_sky_rgb[3], g_tint_prop_rgb[3];
 extern bool g_fog_skybox, g_fog_disable;
 extern int g_fog_rgb[3], g_fog_start, g_fog_end;
diff --git a/src/menu.cpp b/src/menu.cpp
index bdb9531..873f5ed 100644
--- a/src/menu.cpp
+++ b/src/menu.cpp
@@ -64,12 +64,15 @@ FeatureState g_projectiles{true, 0}; // grenade / rocket ESP
 bool g_proj_fuse = true;
 bool g_proj_radius = true;
 FeatureState g_chams{false, 0};
-ChamsGroup g_chams_hostile{true, 3, {255, 60, 60}, true, 3, {255, 60, 60}};
-ChamsGroup g_chams_neutral{true, 3, {220, 220, 220}, false, 3, {220, 220, 220}};
-ChamsGroup g_chams_friendly{true, 3, {60, 255, 60}, false, 3, {60, 255, 60}};
+ChamsGroup g_chams_hostile{true, 3, {255, 60, 60, 255}, true, 3,
+                           {255, 60, 60, 255}};
+ChamsGroup g_chams_neutral{true, 3, {220, 220, 220, 255}, false, 3,
+                           {220, 220, 220, 255}};
+ChamsGroup g_chams_friendly{true, 3, {60, 255, 60, 255}, false, 3,
+                            {60, 255, 60, 255}};
 bool g_chams_viewmodel = false;
 int g_chams_vm_mat = 3;
-int g_chams_vm_rgb[3] = {200, 200, 255};
+int g_chams_vm_rgb[4] = {200, 200, 255, 255};
 bool g_item_health = true;
 bool g_item_ammo = true;
 bool g_item_armor = true;
@@ -244,17 +247,18 @@ void config_save() {
   fprintf(f, "[chams]\nactive=%d\nbind=%d\n", g_chams.active, g_chams.bind);
   auto save_chams = [&](const char *name, const ChamsGroup &g) {
     fprintf(f, "[%s]\nvis=%d\nvis_mat=%d\nvis_r=%d\nvis_g=%d\nvis_b=%d\n"
-               "inv=%d\ninv_mat=%d\ninv_r=%d\ninv_g=%d\ninv_b=%d\n",
+               "vis_a=%d\ninv=%d\ninv_mat=%d\ninv_r=%d\ninv_g=%d\ninv_b=%d\n"
+               "inv_a=%d\n",
             name, (int)g.vis_on, g.vis_mat, g.vis_rgb[0], g.vis_rgb[1],
-            g.vis_rgb[2], (int)g.inv_on, g.inv_mat, g.inv_rgb[0],
-            g.inv_rgb[1], g.inv_rgb[2]);
+            g.vis_rgb[2], g.vis_rgb[3], (int)g.inv_on, g.inv_mat,
+            g.inv_rgb[0], g.inv_rgb[1], g.inv_rgb[2], g.inv_rgb[3]);
   };
   save_chams("chams_hostile", g_chams_hostile);
   save_chams("chams_neutral", g_chams_neutral);
   save_chams("chams_friendly", g_chams_friendly);
-  fprintf(f, "[chams_vm]\non=%d\nmat=%d\nr=%d\ng=%d\nb=%d\n",
+  fprintf(f, "[chams_vm]\non=%d\nmat=%d\nr=%d\ng=%d\nb=%d\na=%d\n",
           (int)g_chams_viewmodel, g_chams_vm_mat, g_chams_vm_rgb[0],
-          g_chams_vm_rgb[1], g_chams_vm_rgb[2]);
+          g_chams_vm_rgb[1], g_chams_vm_rgb[2], g_chams_vm_rgb[3]);
   fprintf(f, "[items]\nactive=%d\nbind=%d\nhealth=%d\nammo=%d\n"
              "armor=%d\nweapons=%d\ncrates=%d\ndistance=%d\nmax_dist=%d\n"
              "usable=%d\n",
@@ -432,11 +436,13 @@ static bool config_load() {
           if (v > 6) v = 6;
           g.vis_mat = v;
         } else if (strcmp(key, "vis_r") == 0 || strcmp(key, "vis_g") == 0 ||
-                   strcmp(key, "vis_b") == 0) {
+                   strcmp(key, "vis_b") == 0 || strcmp(key, "vis_a") == 0) {
           int v = atoi(val);
           if (v < 0) v = 0;
           if (v > 255) v = 255;
-          g.vis_rgb[key[4] == 'r' ? 0 : key[4] == 'g' ? 1 : 2] = v;
+          int idx = key[4] == 'r' ? 0 : key[4] == 'g' ? 1
+                    : key[4] == 'b' ? 2 : 3;
+          g.vis_rgb[idx] = v;
         } else if (strcmp(key, "inv") == 0)
           g.inv_on = atoi(val) != 0;
         else if (strcmp(key, "inv_mat") == 0) {
@@ -445,11 +451,13 @@ static bool config_load() {
           if (v > 6) v = 6;
           g.inv_mat = v;
         } else if (strcmp(key, "inv_r") == 0 || strcmp(key, "inv_g") == 0 ||
-                   strcmp(key, "inv_b") == 0) {
+                   strcmp(key, "inv_b") == 0 || strcmp(key, "inv_a") == 0) {
           int v = atoi(val);
           if (v < 0) v = 0;
           if (v > 255) v = 255;
-          g.inv_rgb[key[4] == 'r' ? 0 : key[4] == 'g' ? 1 : 2] = v;
+          int idx = key[4] == 'r' ? 0 : key[4] == 'g' ? 1
+                    : key[4] == 'b' ? 2 : 3;
+          g.inv_rgb[idx] = v;
         }
       }
       if (in_chams_vm) {
@@ -461,11 +469,13 @@ static bool config_load() {
           if (v > 6) v = 6;
           g_chams_vm_mat = v;
         } else if (strcmp(key, "r") == 0 || strcmp(key, "g") == 0 ||
-                   strcmp(key, "b") == 0) {
+                   strcmp(key, "b") == 0 || strcmp(key, "a") == 0) {
           int v = atoi(val);
           if (v < 0) v = 0;
           if (v > 255) v = 255;
-          g_chams_vm_rgb[key[0] == 'r' ? 0 : key[0] == 'g' ? 1 : 2] = v;
+          int idx = key[0] == 'r' ? 0 : key[0] == 'g' ? 1
+                    : key[0] == 'b' ? 2 : 3;
+          g_chams_vm_rgb[idx] = v;
         }
       }
       if (in_aim) {
@@ -693,14 +703,18 @@ void config_reset_defaults() {
   g_proj_fuse = true;
   g_proj_radius = true;
   g_chams = {false, 0};
-  g_chams_hostile = {true, 3, {255, 60, 60}, true, 3, {255, 60, 60}};
-  g_chams_neutral = {true, 3, {220, 220, 220}, false, 3, {220, 220, 220}};
-  g_chams_friendly = {true, 3, {60, 255, 60}, false, 3, {60, 255, 60}};
+  g_chams_hostile = {true, 3, {255, 60, 60, 255}, true, 3,
+                     {255, 60, 60, 255}};
+  g_chams_neutral = {true, 3, {220, 220, 220, 255}, false, 3,
+                     {220, 220, 220, 255}};
+  g_chams_friendly = {true, 3, {60, 255, 60, 255}, false, 3,
+                      {60, 255, 60, 255}};
   g_chams_viewmodel = false;
   g_chams_vm_mat = 3;
   g_chams_vm_rgb[0] = 200;
   g_chams_vm_rgb[1] = 200;
   g_chams_vm_rgb[2] = 255;
+  g_chams_vm_rgb[3] = 255;
   g_item_health = true;
   g_item_ammo = true;
   g_item_armor = true;
diff --git a/src/studio.cpp b/src/studio.cpp
index bee6db5..07ebec3 100644
--- a/src/studio.cpp
+++ b/src/studio.cpp
@@ -248,6 +248,15 @@ void chams_color(void *mat, float r, float g, float b) {
   vfunc<ColorFn>(mat, 28)(mat, r, g, b);
 }
 
+void chams_alpha(void *mat, float a) {
+  using FindVarFn = void *(*)(void *, const char *, bool *, bool);
+  using SetFloatFn = void (*)(void *, float);
+  bool found = false;
+  void *var = vfunc<FindVarFn>(mat, 11)(mat, "$alpha", &found, false);
+  if (var)
+    vfunc<SetFloatFn>(var, 3)(var, a);
+}
+
 void chams_apply(void *mat, bool ignorez, int style, bool force_white,
                  const int *rgb, bool znearer) {
   using FlagFn = void (*)(void *, int, bool);
@@ -255,10 +264,12 @@ void chams_apply(void *mat, bool ignorez, int style, bool force_white,
   float g = force_white ? 1.0f : (float)rgb[1] / 255.0f;
   float b = force_white ? 1.0f : (float)rgb[2] / 255.0f;
   chams_color(mat, r, g, b);
+  chams_alpha(mat, (float)rgb[3] / 255.0f);
   // 0 Flat, 1 Wireframe, 2 Additive, 3 Solid, 4 White, 5 Fullbright
   // (additive white glow), 6 Glow outline (solid base; the wireframe overlay
   // is a second draw with ZNEARER so its contour is not hidden by the base).
   vfunc<FlagFn>(mat, 29)(mat, 1 << 15 /* IGNOREZ */, ignorez);
+  vfunc<FlagFn>(mat, 29)(mat, 1 << 21 /* TRANSLUCENT */, rgb[3] < 255);
   vfunc<FlagFn>(mat, 29)(mat, 1 << 10 /* ZNEARER */, znearer);
   vfunc<FlagFn>(mat, 29)(mat, 1 << 28 /* WIREFRAME */, style == 1);
   vfunc<FlagFn>(mat, 29)(mat, 1 << 7 /* ADDITIVE */,
@@ -270,12 +281,14 @@ void chams_apply(void *mat, bool ignorez, int style, bool force_white,
 void chams_reset(void *mat) {
   using FlagFn = void (*)(void *, int, bool);
   vfunc<FlagFn>(mat, 29)(mat, 1 << 15, false);
+  vfunc<FlagFn>(mat, 29)(mat, 1 << 21, false);
   vfunc<FlagFn>(mat, 29)(mat, 1 << 10, false);
   vfunc<FlagFn>(mat, 29)(mat, 1 << 28, false);
   vfunc<FlagFn>(mat, 29)(mat, 1 << 7, false);
   vfunc<FlagFn>(mat, 29)(mat, 1 << 12, false);
   vfunc<FlagFn>(mat, 29)(mat, 1 << 6, false);
   chams_color(mat, 1.0f, 1.0f, 1.0f);
+  chams_alpha(mat, 1.0f);
 }
 
 void hkdModelExecute(void *self, const void *state, const void *info,
@@ -306,20 +319,24 @@ void hkdModelExecute(void *self, const void *state, const void *info,
           // Fullbright is an additive, self-illuminated version of the
           // chosen colour: lift it toward white so it reads brighter than
           // the plain additive style.
-          int brgb[3];
+          int brgb[4];
           const int *use_rgb = rgb;
           if (style == 5) {
             for (int i = 0; i < 3; i++)
-              brgb[i] = rgb[i] + (255 - rgb[i]) / 2;
+              brgb[i] = rgb[i] + (255 - rgb[i]) / 4;
+            brgb[3] = rgb[3];
             use_rgb = brgb;
           }
           // Additive blending vanishes against bright backgrounds (sky,
           // white walls, strong fog), which made the viewmodel disappear in
-          // some places. Lay down a dim opaque base first so the first-person
-          // model always has a visible silhouette; the additive pass still
-          // adds the glow on top.
-          if (is_vm && (style == 2 || style == 5)) {
-            int drgb[3] = {rgb[0] / 2, rgb[1] / 2, rgb[2] / 2};
+          // some places. Lay down a faint translucent base so the first-person
+          // model keeps a silhouette on bright backgrounds without turning
+          // into an opaque blob; the additive pass still provides the glow.
+          if (is_vm && (style == 2 || style == 5) && rgb[3] > 0) {
+            int ba = rgb[3] / 8;
+            if (ba < 16)
+              ba = 16;
+            int drgb[4] = {rgb[0], rgb[1], rgb[2], ba};
             chams_apply(mat, ignorez, 3, false, drgb, false);
             g_force_override(self, mat, 0 /* OVERRIDE_NORMAL */);
             g_orig_model_exec(self, state, info, bone);
@@ -333,8 +350,8 @@ void hkdModelExecute(void *self, const void *state, const void *info,
             // the contour and bias it forward so the base cannot bury it.
             void *wire = g_style_mats[1];
             if (wire && wire != mat) {
-              int wrgb[3] = {(rgb[0] + 255) / 2, (rgb[1] + 255) / 2,
-                             (rgb[2] + 255) / 2};
+              int wrgb[4] = {(rgb[0] + 255) / 2, (rgb[1] + 255) / 2,
+                             (rgb[2] + 255) / 2, rgb[3]};
               chams_apply(wire, ignorez, 1, false, wrgb, true);
               g_force_override(self, wire, 0);
               g_orig_model_exec(self, state, info, bone);