![]() ![]() We have loaded the image successfully and the texture id is stored in the cube.id_texture variable. Texture mapping using shaders in OpenGL 3.3 Geometry handling Now we talk about how we use shaders to put texture map on our geometry. That's it for the texture parameter handling. GlTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 4) GlTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_BASE_LEVEL, 0) The parameters to control the total number of mipmaps levels are given by: The OpenGL 3.3 core profile has also deprecated the gluBuild2DMipmaps function. Final parameter is the array of values containing the data elements. the internal layout of the data elements given in the final parameter. Next parameter is the format of our data i.e. Next parameter is the width of border for the texture this enables us to extend the width or height of our texture by an extra set of texels at the borders. The next two parameters are the width and height of our texture. The third parameter is the internal format which we assign as GL_RGBA. The first parameter is the texture target, the second parameter is the mipmap level being loaded (0 is the base level). This function allocates the memory for the texture in memory. GlTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, infoheader.biWidth, infoheader.biHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, l_texture) Next, we issue a call to the glTexImage2D function: We can perform any combination operation we like in the fragment shader with a greater control which makes glTe圎nv call useless. With shaders, we decide the combination of colors ourself. This function allows us to modulate the colors of the texture with those colors that the polygon would have without texture mapping. First, the core profile has removed texture environment modes (glTe圎nv) altogether. There are some subtle changes that we must highlight. GlTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST) GlTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR) GlTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT) GlTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT) The next commands sets the texture parameters GlBindTexture(GL_TEXTURE_2D, num_texture) // Bind the ID texture specified by the 2nd parameter The handling of data and texture parameters is the same as in the fixed funcion pipeline code: The code first issues a call to the LoadBitmap function. To unbind a texture from the texture target, we bind 0 as follows: The texture remains bound to the active texture unit until another call to glBindTexture is made. Following this call, we call glBindTexture to bind our texture to the currently active texture unit. For our case, since we have a single texture, we use the default texture unit i.e. With shaders, you decide directly which texture units you're going to reference by giving a call to glActiveTexture to activate the right texture unit. The glEnable( GL_TEXTURE_2D) function is a directive to the fixed-function pipeline's shader generator that you want to include code to support that texture unit. In a modern core profile, there is no "fixed-function pipeline" (i.e. Now in the OpenGL 3.3 core profile, this call is not needed. In OpenGL versions prior to OpenGL 3.0, we need to explicitly enable the texturing with a call to glEnable like this: The tutorial 3 tells us how to load a bitmap. We are interested in how to handle the textue mapping in OpenGL 3.3 and above. In this tutorial, we see a rotating cube with a texture map applied to it. ![]() In this article, we will learn how to port the 3rd tutorial on texture mapping to the new OpenGL 3.3. 2.4 Where is the texture connected to the uniform sampler?.2 Texture mapping using shaders in OpenGL 3.3. ![]()
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