CODEWITHSUNDEEP
animationwebglshadertextures
Brian A Blackwell
Brian A Blackwell

Reputation: 57

My fragment shader in WebGL program is setting all the colors from my texture to black

I have a simple game that uses three textures with transparent parts. I can see the silhouettes of my textures, but anywhere that doesn't alpha set to zero returns black (0, 0, 0, 1).

Here's my fragment shader:

precision mediump float;

// our texture
uniform sampler2D u_image0;
uniform sampler2D u_image1;
uniform sampler2D u_image2;

// the texCoords passed in from the vertex shader.
varying vec2 v_texCoord;

void main() {
// Look up a color from the texture.
vec4 textureColor = texture2D(u_image0, v_texCoord);
    if (textureColor.a < 0.5) 
        discard;
    else
        gl_FragColor = vec4(textureColor.rgb, textureColor.a);

vec4 textureColor1 = texture2D(u_image1, v_texCoord);
    if (textureColor1.a < 0.5) 
        discard;
    else
        gl_FragColor = vec4(textureColor1.rgb, textureColor1.a);

vec4 textureColor2 = texture2D(u_image2, v_texCoord);
    if (textureColor2.a < 0.5) 
        discard;
    else
        gl_FragColor = vec4(textureColor2.rgb, textureColor2.a);

I got the conditional that tests for alpha from another question, where pixels with zero alpha were being set to white. Solved my problem, but not sure if it scales properly to multiple textures. I'm pretty sure I'm doing it wrong.

Thanks in advance, and let me know if I need to add more code (vertex shader, etc).

Upvotes: 0

Views: 735

Answers (1)

derhass
derhass

Reputation: 45352

It is unclear to me what you actually try to achieve. The way you wrote this code makes me think that you do not know what the discard statement actually does: it completely discards the fragment, the current invocation of the shader will be aborted immediately.

What you shader does is just discard the whole fragment if any of the 3 textures has an alpha value below 0.5. The fact that you have written to gl_FragCoord before doing the discard does not matter at all. If all of the textures have the some alpha above 0.5, the final color will be that of u_image2.

Upvotes: 1

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