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DigiMan Shart

OpenGL Setting an object's color with GLSL

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Right now I'm working with shader's, GLSL, for my program in OpenGL, and I'm trying to set an object's color based off of a color passed into the shader from my OpenGL program. The program implementation somewhat works. The problem is that when I render multiple objects on the screen they all appear to be the same color, despite the fact that I pass in different colors for all the objects. I was wondering if anyone could give me advice on my problem or how to set an object's color based off of a shader. Thanks. Source Code: void cGraphicsManager::InitShaders(GLuint &programId) { static const GLchar* vertexShader = "varying vec3 lightDir,normal;" "void main()" "{" "lightDir = normalize(vec3(gl_LightSource[0].position));" "normal = gl_NormalMatrix * gl_Normal;" "gl_Position = ftransform();" "}"; static const GLchar* pixelShader = "uniform vec4 myColor[5];" "varying vec3 lightDir,normal;" "void main()" "{" "float intensity;" // normalizing the lights position to be on the safe side "vec3 n = normalize(normal);" "intensity = dot(lightDir,n);" "if (intensity > 0.9)" "gl_FragColor = vec4(myColor[0].r, myColor[0].g, myColor[0].b, myColor[0].a);" "else if (intensity > 0.7)" "gl_FragColor = vec4(myColor[1].r, myColor[1].g, myColor[1].b, myColor[1].a);" "else if (intensity > 0.4)" "gl_FragColor = vec4(myColor[2].r, myColor[2].g, myColor[2].b, myColor[2].a);" "else if (intensity > 0.1)" "gl_FragColor = vec4(myColor[3].r, myColor[3].g, myColor[3].b, myColor[3].a);" "else gl_FragColor = vec4(myColor[4].r, myColor[4].g, myColor[4].b, myColor[4].a);" "}"; //Array of our Shader IDs, 0 is Vertex Shader , 1 is Pixel Shader static GLuint shaderId[2]; //GLuint programId; GLint status; char logBuffer[1024]; GLsizei logLength; // ===================== // create vertex shader // ===================== shaderId[0] = glCreateShader(GL_VERTEX_SHADER); glShaderSource(shaderId[0], 1, &vertexShader, 0); glCompileShader(shaderId[0]); glGetShaderiv(shaderId[0], GL_COMPILE_STATUS, &status); if (!status) { glGetShaderInfoLog(shaderId[0], 1024, &logLength, logBuffer); printf("%d | %s\n", logLength, logBuffer); printf("Shader compile error 0!!\n"); glDeleteShader(shaderId[0]); shaderId[0] = 0; return; } // ==================== // create pixel shader // ==================== shaderId[1] = glCreateShader(GL_FRAGMENT_SHADER); glShaderSource (shaderId[1], 1, &pixelShader, 0); glCompileShader (shaderId[1]); glGetShaderiv (shaderId[1], GL_COMPILE_STATUS, &status); if (!status) { glGetShaderInfoLog(shaderId[1], 1024, &logLength, logBuffer); printf("%d | %s\n", logLength, logBuffer); printf("Shader compile error 1!!\n"); glDeleteShader(shaderId[0]); glDeleteShader(shaderId[1]); shaderId[0] = 0; shaderId[1] = 0; return; } // =============== // create program // =============== programId = glCreateProgram(); glAttachShader (programId, shaderId[0]); glAttachShader (programId, shaderId[1]); glLinkProgram (programId); glGetProgramiv (programId, GL_LINK_STATUS, &status); if (!status) { glGetProgramInfoLog(programId, 1024, &logLength, logBuffer); printf("%d | %s\n", logLength, logBuffer); printf("Program link error!!\n"); glDeleteProgram(programId); glDeleteShader(shaderId[0]); glDeleteShader(shaderId[1]); programId = 0; shaderId[0] = 0; shaderId[1] = 0; return; } } /** Renders the scene using shaders. */ void cGraphicsManager::RenderShaders(cObject* obj , GLuint programId) { //If the shader program was created if (programId) { GLuint myColorLocation[5]; glUseProgram(programId); //Find location of variable myColor, which is an array, within shader myColorLocation[0] = glGetUniformLocation(programId, "myColor[0]"); myColorLocation[1] = glGetUniformLocation(programId, "myColor[1]"); myColorLocation[2] = glGetUniformLocation(programId, "myColor[2]"); myColorLocation[3] = glGetUniformLocation(programId, "myColor[3]"); myColorLocation[4] = glGetUniformLocation(programId, "myColor[4]"); if(RenderColor == 1)//Color is Red { //Pass in these parameters to "myColor" glUniform4f(myColorLocation[0], (float)obj->currColor_[0],(float)obj->currColor_[1],(float)obj->currColor_[2],(float)obj->currColor_[3] ); glUniform4f(myColorLocation[1], 0.8f,0.0f,0.0f,1.0f); glUniform4f(myColorLocation[2], 0.6f,0.0f,0.0f,1.0f); glUniform4f(myColorLocation[3], 0.4f,0.0f,0.0f,1.0f ); glUniform4f(myColorLocation[4], 0.2f,0.0f,0.0f,1.0f ); } else if(RenderColor == 2)//Color is Cyan { //Pass in these parameters to "myColor" glUniform4f(myColorLocation[0], (float)obj->currColor_[0],(float)obj->currColor_[1],(float)obj->currColor_[2],(float)obj->currColor_[3] ); glUniform4f(myColorLocation[1], 0.0f,0.8f,0.8f,1.0f); glUniform4f(myColorLocation[2], 0.0f,0.6f,0.6f,1.0f); glUniform4f(myColorLocation[3], 0.0f,0.4f,0.4f,1.0f ); glUniform4f(myColorLocation[4], 0.0f,0.2f,0.2f,1.0f ); } else//Color is white { //Pass in these parameters to "myColor" glUniform4f(myColorLocation[0], (float)obj->currColor_[0],(float)obj->currColor_[1],(float)obj->currColor_[2],(float)obj->currColor_[3] ); glUniform4f(myColorLocation[1], 0.8f,0.8f,0.8f,1.0f); glUniform4f(myColorLocation[2], 0.6f,0.6f,0.6f,1.0f); glUniform4f(myColorLocation[3], 0.4f,0.4f,0.4f,1.0f ); glUniform4f(myColorLocation[4], 0.2f,0.2f,0.2f,1.0f ); } } }

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Instead of writing
gl_FragColor = vec4(myColor[0].r, myColor[0].g, myColor[0].b, myColor[0].a);
you can simply write
gl_FragColor = myColor[0];

Also, I don't know why it is not working for you. Try to update your divers.

If that doesn't work, use a texture that contains the colors your need.


intensity = clamp(dot(lightDir,n), 0.0, 1.0);

gl_FragColor = texture2D(Texture, vec2(intensity, 0.0));

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