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copied!<p>Here's a basic GLUT example (written on OS X, adapt as needed) that generates two checkerboard textures, loads a shader with two samplers and combines them by tinting each (one red, one blue) and blending. See if this works for you:</p> <pre><code>#include <stdio.h> #include <stdlib.h> #include <GLUT/glut.h> #include <OpenGL/gl.h> #include <OpenGL/glu.h> #define kTextureDim 64 GLuint t1; GLuint t2; /* adapted from the red book */ GLuint makeCheckTex() { GLubyte image[kTextureDim][kTextureDim][4]; // RGBA storage for (int i = 0; i < kTextureDim; i++) { for (int j = 0; j < kTextureDim; j++) { int c = ((((i & 0x8) == 0) ^ ((j & 0x8)) == 0))*255; image[i][j][0] = (GLubyte)c; image[i][j][1] = (GLubyte)c; image[i][j][2] = (GLubyte)c; image[i][j][3] = (GLubyte)255; } } GLuint texName; glGenTextures(1, &texName); glBindTexture(GL_TEXTURE_2D, texName); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, kTextureDim, kTextureDim, 0, GL_RGBA, GL_UNSIGNED_BYTE, image); return texName; } void loadShader() { #define STRINGIFY(A) #A const GLchar* source = STRINGIFY( uniform sampler2D tex1; uniform sampler2D tex2; void main() { vec4 s1 = texture2D(tex1, gl_TexCoord[0].st); vec4 s2 = texture2D(tex2, gl_TexCoord[0].st + vec2(0.0625, 0.0625)); gl_FragColor = mix(vec4(1, s1.g, s1.b, 0.5), vec4(s2.r, s2.g, 1, 0.5), 0.5); } ); GLuint program = glCreateProgram(); GLuint shader = glCreateShader(GL_FRAGMENT_SHADER); glShaderSource(shader, 1, &source, NULL); glCompileShader(shader); GLint logLength; glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &logLength); if (logLength > 0) { GLchar* log = (GLchar*)malloc(logLength); glGetShaderInfoLog(shader, logLength, &logLength, log); printf("Shader compile log:\n%s\n", log); free(log); } glAttachShader(program, shader); glLinkProgram(program); glGetProgramiv(program, GL_INFO_LOG_LENGTH, &logLength); if (logLength > 0) { GLchar* log = (GLchar*)malloc(logLength); glGetProgramInfoLog(program, logLength, &logLength, log); printf("Program link log:\n%s\n", log); free(log); } GLuint t1Location = glGetUniformLocation(program, "tex1"); GLuint t2Location = glGetUniformLocation(program, "tex2"); glUniform1i(t1Location, 0); glUniform1i(t2Location, 1); glUseProgram(program); } void init() { glClearColor(0.0, 0.0, 0.0, 0.0); glEnable(GL_DEPTH_TEST); glShadeModel(GL_FLAT); t1 = makeCheckTex(); t2 = makeCheckTex(); loadShader(); } void display() { glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glLoadIdentity(); glActiveTexture(GL_TEXTURE0); glEnable(GL_TEXTURE_2D); glBindTexture(GL_TEXTURE_2D, t1); glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, t2); glBegin(GL_QUADS); //lower left glTexCoord2f(0, 0); glVertex2f(-1.0, -1.0); //upper left glTexCoord2f(0, 1.0); glVertex2f(-1.0, 1.0); //upper right glTexCoord2f(1.0, 1.0); glVertex2f(1.0, 1.0); //lower right glTexCoord2f(1.0, 0); glVertex2f(1.0, -1.0); glEnd(); glutSwapBuffers(); } void reshape(int w, int h) { glViewport(0, 0, w, h); glMatrixMode(GL_PROJECTION); glLoadIdentity(); glOrtho(-2, 2, -2, 2, -2, 2); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); } int main(int argc, char **argv) { glutInit(&argc, argv); glutInitDisplayMode(GLUT_DOUBLE | GLUT_DEPTH | GLUT_RGBA); glutInitWindowSize(512, 512); glutInitWindowPosition(0, 0); glutCreateWindow("GLSL Texture Blending"); glutReshapeFunc(reshape); glutDisplayFunc(display); glutIdleFunc(display); init(); glutMainLoop(); return 0; } </code></pre> <p>Hopefully the result will look something like this (you can comment out the <code>glUseProgram</code> call to see the first texture drawn without the shader): <img src="https://i.stack.imgur.com/nqQTQ.png" alt="alt text"></p>

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