the internalformat of Texture
graphics, opengl
Solution
The `format` and `type` parameters describe the data you are passing to OpenGL as part of a pixel transfer operation. The `internalformat` describes the format of the texture. You're telling OpenGL that you're giving it takes that looks like X, and OpenGL is to store it in a texture where the data is Y. The `internalformat` is "Y".
The `GL_LUMINANCE8` internal format represents a normalized unsigned integer format. This means that the data is conceptually floating-point, but stored in a normalized integer form as a means of compression.
For that matter, the `format` of `GL_LUMINANCE` says that you're passing either floating-point data or normalized integer data (the `type` says that it's normalized integer data). Of course, since there's no `GL_LUMINANCE_INTEGER` (which is how you say that you're passing integer data, to be used with integer internal formats), you can't really use luminance data like this.
Use `GL_RED_INTEGER` for the format and `GL_R8UI` for the internal format if you really want 8-bit unsigned integers in your texture. Note that integer texture support requires OpenGL 3.x-class hardware.
That being said, you cannot use `sampler2D` with an integer texture. If you are using a texture that uses an unsigned integer texture format, you must use `usampler2D`.
Problem
Look at the following OpenGL function: ``` void glTexImage2D(GLenum target, GLint level, GLint internalFormat, GLsizei width, GLsizei height, GLint border, GLenum format, GLenum type, const GLvoid * data); ``` I know the parameter format and type describe the format and type of the image data,but I don't understand the prameter internalFormat.How should I set its value in my application? For example,I create a texture like this: ``` glTexImage2D(GL_TEXTURE_2D,0,GL_LUMINANCE8,size,size,0,GL_LUMINANCE,GL_UNSIGNED_BYTE,buffer); ``` When I aceess the texture in it in my GLSL shader,it seems that the value that I get is between [0,1].WHy?Shouldn't it between [0,255]? Part of My shader code is : ``` vec = EntryPoint + delta_dir * texture(noiseTex,EntryPoint.xy * 32).x; ``` Part of my C++ Code : ``` for (int i = 0;i < temp;++i) { buffer[i] = 255.0 * rand() / (float)RAND_MAX; } glGenTextures(1,&noiseTex); glActiveTexture(GL_TEXTURE0 + activeTexUnit); glBindTexture(GL_TEXTURE_2D,noiseTex); glTexImage2D(GL_TEXTURE_2D,0,GL_LUMINANCE8,size,size, 0,GL_LUMINANCE,GL_UNSIGNED_BYTE,buffer); 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_MIN_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); ```