X-Git-Url: https://git.lukelau.me/?p=clouds.git;a=blobdiff_plain;f=billboardfrag.glsl;h=2349e4dfef4610558042a9f6b8315e1ac217800a;hp=840ec895609039c2989a77f69b2d56c12448e910;hb=31f19438c73b207f506ba0b1187d2de75c166a5b;hpb=69b74f1d5e67236a5396b75628a6e1be0e501631

diff --git a/billboardfrag.glsl b/billboardfrag.glsl
index 840ec89..2349e4d 100644
--- a/billboardfrag.glsl
+++ b/billboardfrag.glsl
@@ -3,7 +3,25 @@ uniform vec4 color;
 uniform sampler2D tex;
 in vec2 texCoord;
 out vec4 FragColor;
+uniform bool modulate;
 void main() {
-  FragColor = texture(tex, texCoord).r * color;
+	// Cf = color from fragment, Ct = color from texture
+	// Cc = color from texture environment(?) assume to be 0?
+	// Af = alpha from fragment, At = alpha from texture
+	// C = output color, A = output alpha
+	float f = texture(tex, texCoord).r;
+	if (modulate) { 
+		// GL_MODULATE: C
+		// C = Cf * Ct
+		// A = Af * At				
+		FragColor = color * f;
+	} else {
+		// GL_BLEND:
+		// C = Cf * (1-Ct) + Cc * Ct
+		// A = Af * At
+		vec3 C = color.rgb * (1 - f);
+		float A = color.a * f;
+		FragColor = vec4(C, A);
+	}
 }