Add replace alpha option to decals

1 files changed, 55 insertions, 1 deletions

diff --git a/decal.cginc b/decal.cginc
index a2092da..e917fdf 100644
--- a/decal.cginc
+++ b/decal.cginc
@@ -27,6 +27,58 @@ float2 decal_rotate(float2 uv, float rotation) {
   return float2(d.x * c - d.y * s, d.x * s + d.y * c) + 0.5;
 }
 
+#if defined(_DECAL0_REPLACE_ALPHA)
+#define APPLY_DECAL_REPLACE_ALPHA_0 pbr.albedo.a = lerp(albedo_alpha_before_decal, decal_alpha_at_full_opacity, _Decal0_Opacity);
+#else
+#define APPLY_DECAL_REPLACE_ALPHA_0
+#endif
+#if defined(_DECAL1_REPLACE_ALPHA)
+#define APPLY_DECAL_REPLACE_ALPHA_1 pbr.albedo.a = lerp(albedo_alpha_before_decal, decal_alpha_at_full_opacity, _Decal1_Opacity);
+#else
+#define APPLY_DECAL_REPLACE_ALPHA_1
+#endif
+#if defined(_DECAL2_REPLACE_ALPHA)
+#define APPLY_DECAL_REPLACE_ALPHA_2 pbr.albedo.a = lerp(albedo_alpha_before_decal, decal_alpha_at_full_opacity, _Decal2_Opacity);
+#else
+#define APPLY_DECAL_REPLACE_ALPHA_2
+#endif
+#if defined(_DECAL3_REPLACE_ALPHA)
+#define APPLY_DECAL_REPLACE_ALPHA_3 pbr.albedo.a = lerp(albedo_alpha_before_decal, decal_alpha_at_full_opacity, _Decal3_Opacity);
+#else
+#define APPLY_DECAL_REPLACE_ALPHA_3
+#endif
+#if defined(_DECAL4_REPLACE_ALPHA)
+#define APPLY_DECAL_REPLACE_ALPHA_4 pbr.albedo.a = lerp(albedo_alpha_before_decal, decal_alpha_at_full_opacity, _Decal4_Opacity);
+#else
+#define APPLY_DECAL_REPLACE_ALPHA_4
+#endif
+#if defined(_DECAL5_REPLACE_ALPHA)
+#define APPLY_DECAL_REPLACE_ALPHA_5 pbr.albedo.a = lerp(albedo_alpha_before_decal, decal_alpha_at_full_opacity, _Decal5_Opacity);
+#else
+#define APPLY_DECAL_REPLACE_ALPHA_5
+#endif
+#if defined(_DECAL6_REPLACE_ALPHA)
+#define APPLY_DECAL_REPLACE_ALPHA_6 pbr.albedo.a = lerp(albedo_alpha_before_decal, decal_alpha_at_full_opacity, _Decal6_Opacity);
+#else
+#define APPLY_DECAL_REPLACE_ALPHA_6
+#endif
+#if defined(_DECAL7_REPLACE_ALPHA)
+#define APPLY_DECAL_REPLACE_ALPHA_7 pbr.albedo.a = lerp(albedo_alpha_before_decal, decal_alpha_at_full_opacity, _Decal7_Opacity);
+#else
+#define APPLY_DECAL_REPLACE_ALPHA_7
+#endif
+
+#if defined(_DECAL0_REPLACE_ALPHA) || defined(_DECAL1_REPLACE_ALPHA) || defined(_DECAL2_REPLACE_ALPHA) || defined(_DECAL3_REPLACE_ALPHA) || defined(_DECAL4_REPLACE_ALPHA) || defined(_DECAL5_REPLACE_ALPHA) || defined(_DECAL6_REPLACE_ALPHA) || defined(_DECAL7_REPLACE_ALPHA)
+#define PREPARE_DECAL_REPLACE_ALPHA \
+  float albedo_alpha_before_decal = pbr.albedo.a; \
+  float decal_alpha_at_full_opacity = albedo.a;
+#else
+#define PREPARE_DECAL_REPLACE_ALPHA
+#endif
+
+#define APPLY_DECAL_REPLACE_ALPHA_IMPL(N) APPLY_DECAL_REPLACE_ALPHA_##N
+#define APPLY_DECAL_REPLACE_ALPHA(N) APPLY_DECAL_REPLACE_ALPHA_IMPL(N)
+
 #define APPLY_DECAL(N) \
   { \
     float2 uv = get_uv_by_channel(i, _Decal##N##_UV_Channel); \
@@ -43,7 +95,6 @@ float2 decal_rotate(float2 uv, float rotation) {
       albedo.a = smoothstep(-w, w, d); \
     } \
     albedo *= _Decal##N##_Color; \
-    albedo.a *= _Decal##N##_Opacity; \
     if (_Decal##N##_Mask_Enabled) { \
       float2 mask_uv = get_uv_by_channel(i, _Decal##N##_Mask_UV_Channel); \
       mask_uv -= _Decal##N##_Mask_ST.zw; \
@@ -52,6 +103,8 @@ float2 decal_rotate(float2 uv, float rotation) {
       if (_Decal##N##_Mask_Invert) mask = 1 - mask; \
       albedo.a *= mask; \
     } \
+    PREPARE_DECAL_REPLACE_ALPHA \
+    albedo.a *= _Decal##N##_Opacity; \
     if (_Decal##N##_Albedo_Clamp) albedo.rgb = saturate(albedo.rgb); \
     [forcecase] \
     switch (_Decal##N##_Mix_Mode) { \
@@ -65,6 +118,7 @@ float2 decal_rotate(float2 uv, float rotation) {
         pbr.albedo.rgb += lerp(0, albedo.rgb * pbr.albedo.rgb, albedo.a); \
         break; \
     } \
+    APPLY_DECAL_REPLACE_ALPHA(N) \
     if (_Decal##N##_Metallic_Gloss_Enabled) { \
       float4 mg = decal_sample(_Decal##N##_Metallic_Gloss, uv, _Decal##N##_UV_Mode); \
       pbr.metallic = lerp(pbr.metallic, mg.r * _Decal##N##_Metallic, albedo.a); \