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POTrouble displaying texture in OpenGL ES with C++
 

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  1. POTrouble displaying texture in OpenGL ES with C++
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    <p>I'm trying to write a small, portable 2D engine for iOS to learn C++ and OpenGL. Right now I'm trying to display a texture that I've loaded in. I've been successful displaying a texture when loading in the with CoreGraphic libraries, but now I'm trying to load the file in C++ with fread and libpng and all I see is a white box.</p> <p>My texture is 64x64 so it's not a power of 2 problem. Also I have enabled GL_TEXTURE_2D.</p> <p>The first block of code is used to load the png, convert the png to image data, and load the data into OpenGL. </p> <pre><code>void AssetManager::loadImage(const std::string &amp;filename) { Texture texture(filename); png_structp png_ptr = NULL; png_infop info_ptr = NULL; png_bytep *row_pointers = NULL; int bitDepth, colourType; FILE *pngFile = fopen(std::string(Game::environmentData.basePath + "/" + filename).c_str(), "rb"); if(!pngFile) return; png_byte sig[8]; fread(&amp;sig, 8, sizeof(png_byte), pngFile); rewind(pngFile);//so when we init io it won't bitch if(!png_check_sig(sig, 8)) return; png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL,NULL,NULL); if(!png_ptr) return; if(setjmp(png_jmpbuf(png_ptr))) return; info_ptr = png_create_info_struct(png_ptr); if(!info_ptr) return; png_init_io(png_ptr, pngFile); png_read_info(png_ptr, info_ptr); bitDepth = png_get_bit_depth(png_ptr, info_ptr); colourType = png_get_color_type(png_ptr, info_ptr); if(colourType == PNG_COLOR_TYPE_PALETTE) png_set_palette_to_rgb(png_ptr); /*if(colourType == PNG_COLOR_TYPE_GRAY &amp;&amp; bitDepth &lt; 8) png_set_gray_1_2_4_to_8(png_ptr);*/ if(png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) png_set_tRNS_to_alpha(png_ptr); if(bitDepth == 16) png_set_strip_16(png_ptr); else if(bitDepth &lt; 8) png_set_packing(png_ptr); png_read_update_info(png_ptr, info_ptr); png_get_IHDR(png_ptr, info_ptr, &amp;texture.width, &amp;texture.height, &amp;bitDepth, &amp;colourType, NULL, NULL, NULL); int components = GetTextureInfo(colourType); if(components == -1) { if(png_ptr) png_destroy_read_struct(&amp;png_ptr, &amp;info_ptr, NULL); return; } GLubyte *pixels = (GLubyte *)malloc(sizeof(GLubyte) * (texture.width * texture.height * components)); row_pointers = (png_bytep *)malloc(sizeof(png_bytep) * texture.height); for(int i = 0; i &lt; texture.height; ++i) row_pointers[i] = (png_bytep)(pixels + (i * texture.width * components)); png_read_image(png_ptr, row_pointers); png_read_end(png_ptr, NULL); // make it glGenTextures(1, &amp;texture.name); // bind it glBindTexture(GL_TEXTURE_2D, texture.name); GLuint glcolours; switch (components) { case 1: glcolours = GL_LUMINANCE; break; case 2: glcolours = GL_LUMINANCE_ALPHA; break; case 3: glcolours = GL_RGB; break; case 4: glcolours = GL_RGBA; break; } glTexImage2D(GL_TEXTURE_2D, 0, components, texture.width, texture.height, 0, glcolours, GL_UNSIGNED_BYTE, pixels); 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_LINEAR); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); png_destroy_read_struct(&amp;png_ptr, &amp;info_ptr, NULL); fclose(pngFile); free(row_pointers); free(pixels); textures.push_back(texture); } </code></pre> <p>Here is the code for my Texture class:</p> <pre><code>class Texture { public: Texture(const std::string &amp;filename) { this-&gt;filename = filename; } unsigned int name; unsigned int size; unsigned int width; unsigned int height; std::string filename; }; </code></pre> <p>Here is how I setup my view:</p> <pre><code>void Renderer::Setup(Rectangle rect, CameraType cameraType) { _viewRect = rect; glViewport(0,0,_viewRect.width,_viewRect.height); if(cameraType == Renderer::Orthographic) { glMatrixMode(GL_PROJECTION); glLoadIdentity(); glOrthof(_viewRect.x,_viewRect.width,_viewRect.y,_viewRect.height,kZNear,kZFar); glMatrixMode(GL_MODELVIEW); } else { GLfloat size = kZNear * tanf(DegreesToRadians(kFieldOfView) / 2.0); glEnable(GL_DEPTH_TEST); glMatrixMode(GL_PROJECTION); glLoadIdentity(); glFrustumf(-size, size, -size / (_viewRect.width / _viewRect.height), size / (_viewRect.width / _viewRect.height), kZNear, kZFar); glMatrixMode(GL_MODELVIEW); } glEnable(GL_TEXTURE_2D); glBlendFunc(GL_ONE, GL_SRC_COLOR); glEnable(GL_BLEND); } </code></pre> <p>Now here is where I draw the texture:</p> <pre><code>void Renderer::DrawTexture(int x, int y, Texture &amp;texture) { GLfloat vertices[] = { x, _viewRect.height - y, 0.0, x, _viewRect.height - (y + texture.height), 0.0, x + texture.width, _viewRect.height - y, 0.0, x + texture.width, _viewRect.height - (y + texture.height), 0.0 }; static const GLfloat normals[] = { 0.0, 0.0, 1.0, 0.0, 0.0, 1.0, 0.0, 0.0, 1.0, 0.0, 0.0, 1.0 }; GLfloat texCoords[] = { 0.0, 1.0, 0.0, 0.0, 1.0, 1.0, 1.0, 0.0 }; glEnableClientState(GL_VERTEX_ARRAY); glEnableClientState(GL_NORMAL_ARRAY); glEnableClientState(GL_TEXTURE_COORD_ARRAY); glLoadIdentity(); glTranslatef(0.0, 0.0, -3.0); glBindTexture(GL_TEXTURE_2D, texture.name); glVertexPointer(3, GL_FLOAT, 0, vertices); glNormalPointer(GL_FLOAT, 0, normals); glTexCoordPointer(2, GL_FLOAT, 0, texCoords); glDrawArrays(GL_TRIANGLE_STRIP, 0, 4); glDisableClientState(GL_VERTEX_ARRAY); glDisableClientState(GL_NORMAL_ARRAY); glDisableClientState(GL_TEXTURE_COORD_ARRAY); } </code></pre> <p><strong>UPDATE:</strong></p> <p>I changed the function I use to generate a texture. It now create a random test texture. I still see a white texture no matter what. Gonna keep digging into how I'm renderering.</p> <p>Here's the new function:</p> <pre><code>void AssetManager::CreateNoisyTexture(const char * key) { Texture texture(key, 64, 64); const unsigned int components = 4; GLubyte *pixels = (GLubyte *)malloc(sizeof(GLubyte) * (texture.width * texture.height * components)); GLubyte *pitr1 = pixels; GLubyte *pitr2 = pixels + (texture.width * texture.height * components); while (pitr1 != pitr2) { *pitr1 = rand() * 0xFF; *(pitr1 + 1) = rand() * 0xFF; *(pitr1 + 2) = rand() * 0xFF; *(pitr1 + 3) = 0xFF; pitr1 += 4; } glGenTextures(1, &amp;texture.name); glBindTexture(GL_TEXTURE_2D, texture.name); glTexImage2D(GL_TEXTURE_2D, 0, components, texture.width, texture.height, 0, GL_RGBA, GL_UNSIGNED_BYTE, pixels); 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); free(pixels); printf("Created texture with key: %s name: %d", texture.key, texture.name); textures.push_back(texture); } </code></pre>
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    1. PO
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    1. USMeroon
    1. USMeroon
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      1. POTrouble displaying texture in OpenGL ES with C++
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      1. VTUpMod
    2. VO
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      1. POTrouble displaying texture in OpenGL ES with C++
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      1. VTUpMod
    1. COAre you sure that the PNG decompression is working correctly? I would start by generating a RGBA texture in memory and try using that first. Something simple like half red and half green would work. It should help narrow down where the problem is.
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      1. POTrouble displaying texture in OpenGL ES with C++
      1. USIronMensan
    2. COA couple of nits: the `name` member of `Texture` should be `GLuint`, not `unsigned int`. And you can remove setting `GL_TEXTURE_MIN_FILTER` to `GL_LINEAR` since you are changing it to `GL_NEAREST` immediately afterwards.
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      1. POTrouble displaying texture in OpenGL ES with C++
      1. USIronMensan
    3. COThanks for the feedback! I'll give that a shot tonight and let you know.
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      1. POTrouble displaying texture in OpenGL ES with C++
      1. USMeroon
 

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