graphics: model: Add basic alpha mode support for glTF models.

1 files changed, 22 insertions, 0 deletions

diff --git a/data/shaders/pbr-frag.glsl b/data/shaders/pbr-frag.glsl
index ce252ab..5b21fe1 100644
--- a/data/shaders/pbr-frag.glsl
+++ b/data/shaders/pbr-frag.glsl
@@ -15,6 +15,7 @@ struct Material {
   vec3 emissiveFactor;
   bool emissiveTextureEnabled;
   int emissiveTexcoord;
+  int alphaMode;
   float alphaCutoff;
 };
 
@@ -49,6 +50,25 @@ vec4 sampleTexture(sampler2D tex, bool enabled, int texcoord, vec3 factor, vec4
   }
 }
 
+vec4 applyAlpha(vec4 color) {
+  // Apply alpha mode.
+  if(material.alphaMode == 0) {
+    return vec4(color.xyz, 1.0);
+  } else if(material.alphaMode == 1) {
+    if(color.a >= material.alphaCutoff) {
+      return vec4(color.xyz, 1.0);
+    } else {
+      discard;
+    }
+  } else if(material.alphaMode == 2) {
+    if(color.a <= 0.005) {
+      discard;
+    } else {
+      return color;
+    }
+  }
+}
+
 void main(void) {
   vec4 finalColor = sampleTexture(baseColorTexture,
                                   material.baseColorTextureEnabled,
@@ -77,6 +97,8 @@ void main(void) {
                               material.emissiveTexcoord,
                               material.emissiveFactor,
                               vec4(0.0, 0.0, 0.0, 0.0));
+  finalColor = applyAlpha(finalColor);
+
 #ifdef GLSL330
   fragColor = finalColor;
 #else