I have two textures, cloud and hill, each with 512 x 512 size, and i intend to create a gl_FragColor output which will obtain the pixel values from the previous textures. In this case, i want to obtain the 1st pixel in gl_FragColor
from the 1st pixel in the 1st texture, the 2nd pixel in the gl_FragColor
from the 2nd pixel in the 2nd texture, the 3rd pixel in gl_FragColor
from the 3rd pixel in the 1st texture an so on. Here is my fragment shader code:
uniform sampler2D tex0;
uniform sampler2D tex1;
void main() {
vec4 cloud = texture2D(tex0, gl_TexCoord[0].st);
vec4 hill = texture2D(tex1, gl_TexCoord[0].st);
for (int i=0;i<512;i++) {
for (int j=0;j<512;j++) {
if ( j%2 == 0)
gl_FragColor = cloud;
else
gl_FragColor = hill;
}
}
}
Here's the texture unit setup:
t1 = loadTexture("pY.raw", 512, 512);
t2 = loadTexture("pZ.raw", 512, 512);
glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, t2);
glEnable(GL_TEXTURE_2D);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, t1);
glEnable(GL_TEXTURE_2D);
And here is the uniform setup: glUseProgram(program);
GLuint t1Location = glGetUniformLocation(program, "tex0");
GLuint t2Location = glGetUniformLocation(program, "tex1");
glUniform1i(t1Location, 0);
glUniform1i(t2Location, 1);
The problem is, the output for the program is only the hill texture, and i don't know how to fix this. Any suggestion?
You don't need to do any iterations in your shader. Pixel shader will be called once for every pixel in your object. Instead use gl_TexCoord[0] to get current texture coordinates. Your code should look something like that:
uniform sampler2D tex0;
uniform sampler2D tex1;
void main()
{
vec4 cloud = texture2D(tex0, gl_TexCoord[0].st);
vec4 hill = texture2D(tex1, gl_TexCoord[0].st);
if ( int(gl_TexCoord[0].x*512)%2 == 0)
gl_FragColor = cloud;
else
gl_FragColor = hill;
}
}
This one should work, even with older opengl:
#ifdef GL_ES
precision highp float;
#endif
uniform sampler2D tex0;
uniform sampler2D tex1;
void main(void)
{
if((gl_FragCoord/32.0- vec4(ivec4(gl_FragCoord/32.0))).x<0.5)
gl_FragColor = texture2D(tex0, gl_FragCoord.xy/512.0);
else
gl_FragColor = texture2D(tex1, gl_FragCoord.xy/512.0);
}
You can try it out with WebGL at: http://www.iquilezles.org/apps/shadertoy/