Question

I wrote this code:

"    vec3 col1 = texture2D(uDiffuseTexture, vec2(vTextureCoord.x, vTextureCoord.y + time)).rgb;\n" +
"    float a1=1.0;\n"+  
"    vec3 col2 = texture2D(uNormalTexture, vec2(vTextureCoord.x + time, vTextureCoord.y)).rgb;\n" +
"    float a2=uAlpha;\n"+  

by the way:

with: gl_FragColor = vec4(col1+col2, a1+a2);

alpha not working…why? always the same, why?

my uAlpha variable is an uniform, that changes from 0.1 to 1.0

Answer 1

i d like to draw image1 with 100%, and image2 with 0-100%

Currently, you’re mixing your two images with additive blending (col1+col2) without considering the uAlpha uniform to mix the two images.

I suppose that what you’re trying to achieve is blend image2 over image1, using uAlpha as opacity.

vec3 col1 = texture2D(uDiffuseTexture, vec2(vTextureCoord.x, vTextureCoord.y + time)).rgb;
vec3 col2 = texture2D(uNormalTexture, vec2(vTextureCoord.x + time, vTextureCoord.y)).rgb;
float a2=uAlpha;
vec3 result = mix(col1, col2, a2);   // this combines the two texture colors
gl_FragColor = vec4(result, 1.0);