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POSDL 3d OpenGL: texture on cube produces blank screen
 

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  1. POSDL 3d OpenGL: texture on cube produces blank screen
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    <p>I have been trying to load a texture on to a cube using SDL_image and OpenGL. For some reason, the entire window remains blank when I attempt to use textures. By commenting out my texture initialisation call, the window renders as it should, except with a white texture. The same applies when my call to glEnable(GL_TEXTURE_2D) gets commented out. I have been trying for several hours now to fix this, and have spent most of those looking online for whether anyone has come up with a solution, but nothing I tried worked. I have posted only sections of my code below, if more is required, please let me know.</p> <p>OpenGL initialisation (The order for glEnable(GL_TEXTURE_2D) may be incorrect):</p> <pre><code>//Configures OpenGL for 3d rendering //Needs to know the window height and width void setUpOpenGL(int width, int height) { //Enable depth testing, necessary for 3d worlds glEnable(GL_DEPTH_TEST); glEnable(GL_TEXTURE_2D); //Set the background colour to black glClearColor(0.0f, 0.0f, 0.0f, 1.0f); //Set the clear depth at 1m? glClearDepth(1.0f); //Configure the viewport, giving height and width glViewport(0, 0, width, height); //Clear the colour buffer glClear(GL_COLOR_BUFFER_BIT); //Initiate OpenGL for projection drawing glMatrixMode(GL_PROJECTION); //Load identity, purpose still unknown glLoadIdentity(); //Initiate viewport as perspective, give the field of view, aspect ratio (width/height), minimum distance and maximum distance gluPerspective(45.0f, (float)width / (float)height, 0.01f, 500.0f); //Initiate OpenGL for model drawing, preparation for frame rendering glMatrixMode(GL_MODELVIEW); //Load identity again (identity matrix?) glLoadIdentity(); //Set the shading model to smooth. Other options feasable, but don't look as good glShadeModel(GL_SMOOTH); //For whatever reason, we need to state how to calculate depth. Grouped under "Alpha Function" glDepthFunc(GL_LEQUAL); //Calculate perspective as "nicest"; "don't care" and "fastest" are other options glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST); //Finished configuring OpenGL return; } </code></pre> <p>Here my loadTexture function (errorCode remains 0 through the entire function, and nothing is printed to stderr):</p> <pre><code>//Function to load textures from file. Needs to know the filename / relative location. //Load textures from file int loadTexture(char *filename) { GLuint returnValue = -1; SDL_Surface *image; void *raw; int width, height, bpp; Uint8 *srcPixel, *dstPixel; Uint32 truePixel; GLenum errorCode; image = IMG_Load(filename); if(!image) { fprintf(stderr, "Warning: Error loading image %s: %s\n", filename, IMG_GetError()); return -2; } if(image-&gt;format-&gt;BytesPerPixel &lt; 2) { fprintf(stderr, "Warning: %s is a bad image, not true colour\n", filename); return -3; } width = image-&gt;w; height = image-&gt;h; raw = (void *)malloc(width * height * 4); dstPixel = (Uint8 *)raw; SDL_LockSurface(image); bpp = image-&gt;format-&gt;BytesPerPixel; for(int i = height - 1; i &gt;= 0; i--) { for(int j = 0; j &lt; width; j++) { srcPixel = (Uint8 *)image-&gt;pixels + i * image-&gt;pitch + j * bpp; switch(bpp) { case 1: truePixel = *srcPixel; break; case 2: truePixel = *(Uint16 *)srcPixel; break; case 3: if(SDL_BYTEORDER == SDL_BIG_ENDIAN) truePixel = srcPixel[0] &lt;&lt; 16 | srcPixel[1] &lt;&lt; 8 | srcPixel[2]; else truePixel = srcPixel[0] | srcPixel[1] &lt;&lt; 8 | srcPixel[2] &lt;&lt; 16; break; case 4: truePixel = *(Uint32 *)srcPixel; break; default: fprintf(stderr, "Warning: image BPP of %d in image %s unuseable\n", bpp, filename); SDL_UnlockSurface(image); SDL_FreeSurface(image); free(raw); return -4; } SDL_GetRGBA(truePixel, image-&gt;format, &amp;(dstPixel[0]), &amp;(dstPixel[1]), &amp;(dstPixel[2]), &amp;(dstPixel[3])); dstPixel++; dstPixel++; dstPixel++; dstPixel++; } } SDL_UnlockSurface(image); SDL_FreeSurface(image); while(glGetError()); glGenTextures(1, &amp;returnValue); glBindTexture(GL_TEXTURE_2D, returnValue); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR/*_MIPMAP_LINEAR*/); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); //glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_TRUE); glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE); glTexImage2D(GL_TEXTURE_2D, 0, 4, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, (Uint8 *)raw); errorCode = glGetError(); if(errorCode) { if(errorCode == GL_OUT_OF_MEMORY) fprintf(stderr, "Warning: Texture memory full while binding texture from image %s\n", filename); else fprintf(stderr, "OpenGL error while creating texture: %d", (int)errorCode); glDeleteTextures(1, &amp;returnValue); free(raw); return -5; } //gluBuild2DMipmaps(GL_TEXTURE_2D, 4, width, height, GL_RGBA, GL_UNSIGNED_BYTE, (Uint8 *)raw); errorCode = glGetError(); if(errorCode) { if(errorCode == GL_OUT_OF_MEMORY) fprintf(stderr, "Warning: Texture memory full while building texture from image %s\n", filename); else fprintf(stderr, "OpenGL error while creating texture: %s", (int)errorCode); glDeleteTextures(1, &amp;returnValue); free(raw); return -6; } return returnValue; } </code></pre> <p>Finally, my actual render code. Note that the return value for the loadTexture function is copied into all elements of the texture array (right, left, top, bottom, front, back (enums)).</p> <pre><code>void cube::render(void) { float xMinOffset, xMaxOffset, yMinOffset, yMaxOffset, zMinOffset, zMaxOffset; //getoffset(xMinOffset, xMaxOffset, yMinOffset, yMaxOffset, zMinOffset, zMaxOffset); xMinOffset = yMinOffset = zMinOffset = 0.0f; xMaxOffset = yMaxOffset = zMaxOffset = 1.0f; //Positive x, or right glBegin(GL_QUADS); { glColor3f(1.0f, 1.0f, 1.0f); glNormal3f(1.0f, 0.0f, 0.0f); glBindTexture(GL_TEXTURE_2D, texture[right]); glTexCoord2f(0.0f, 1.0f); glVertex3f(xMaxOffset, yMinOffset, zMinOffset); glTexCoord2f(1.0f, 1.0f); glVertex3f(xMaxOffset, yMinOffset, zMaxOffset); glTexCoord2f(1.0f, 0.0f); glVertex3f(xMaxOffset, yMaxOffset, zMaxOffset); glTexCoord2f(0.0f, 0.0f); glVertex3f(xMaxOffset, yMaxOffset, zMinOffset); } glEnd(); //Negative x, or left glBegin(GL_QUADS); { glColor3f(1.0f, 1.0f, 1.0f); glNormal3f(-1.0f, 0.0f, 0.0f); glBindTexture(GL_TEXTURE_2D, texture[left]); glTexCoord2f(0.0f, 1.0f); glVertex3f(xMinOffset, yMinOffset, zMinOffset); glTexCoord2f(1.0f, 1.0f); glVertex3f(xMinOffset, yMinOffset, zMaxOffset); glTexCoord2f(1.0f, 0.0f); glVertex3f(xMinOffset, yMaxOffset, zMaxOffset); glTexCoord2f(0.0f, 0.0f); glVertex3f(xMinOffset, yMaxOffset, zMinOffset); } glEnd(); //Positive y, or top glBegin(GL_QUADS); { glColor3f(1.0f, 1.0f, 1.0f); glNormal3f(0.0f, 1.0f, 0.0f); glBindTexture(GL_TEXTURE_2D, texture[top]); glTexCoord2f(1.0f, 1.0f); glVertex3f(xMinOffset, yMaxOffset, zMinOffset); glTexCoord2f(1.0f, 0.0f); glVertex3f(xMinOffset, yMaxOffset, zMaxOffset); glTexCoord2f(0.0f, 0.0f); glVertex3f(xMaxOffset, yMaxOffset, zMaxOffset); glTexCoord2f(0.0f, 1.0f); glVertex3f(xMaxOffset, yMaxOffset, zMinOffset); } glEnd(); //Negative y, or bottom glBegin(GL_QUADS); { glColor3f(1.0f, 1.0f, 1.0f); glNormal3f(0.0f, -1.0f, 0.0f); glBindTexture(GL_TEXTURE_2D, texture[bottom]); glTexCoord2f(1.0f, 1.0f); glVertex3f(xMinOffset, yMinOffset, zMinOffset); glTexCoord2f(1.0f, 0.0f); glVertex3f(xMinOffset, yMinOffset, zMaxOffset); glTexCoord2f(0.0f, 0.0f); glVertex3f(xMaxOffset, yMinOffset, zMaxOffset); glTexCoord2f(0.0f, 1.0f); glVertex3f(xMaxOffset, yMinOffset, zMinOffset); } glEnd(); //Positive z, or front glBegin(GL_QUADS); { glColor3f(1.0f, 1.0f, 1.0f); glNormal3f(0.0f, 0.0f, 1.0f); glBindTexture(GL_TEXTURE_2D, texture[front]); glTexCoord2f(0.0f, 1.0f); glVertex3f(xMinOffset, yMinOffset, zMaxOffset); glTexCoord2f(0.0f, 0.0f); glVertex3f(xMinOffset, yMaxOffset, zMaxOffset); glTexCoord2f(1.0f, 0.0f); glVertex3f(xMaxOffset, yMaxOffset, zMaxOffset); glTexCoord2f(1.0f, 1.0f); glVertex3f(xMaxOffset, yMinOffset, zMaxOffset); } glEnd(); //Negative z, or back glBegin(GL_QUADS); { glColor3f(1.0f, 1.0f, 1.0f); glNormal3f(0.0f, 0.0f, -1.0f); glBindTexture(GL_TEXTURE_2D, texture[back]); glTexCoord2f(1.0f, 1.0f); glVertex3f(xMinOffset, yMinOffset, zMinOffset); glTexCoord2f(1.0f, 0.0f); glVertex3f(xMinOffset, yMaxOffset, zMinOffset); glTexCoord2f(0.0f, 0.0f); glVertex3f(xMaxOffset, yMaxOffset, zMinOffset); glTexCoord2f(0.0f, 1.0f); glVertex3f(xMaxOffset, yMinOffset, zMinOffset); } glEnd(); } </code></pre> <p>And here the render function, along with some other drawing-related functions. Note that initDisplayLists() is called in initialisation.</p> <pre><code>void redraw(void) { //Still has the data from the previous frame //Clear the colour and depth buffers before rendering glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); //Load identity, purpose unknown glLoadIdentity(); //Draw horizontal crosshair glBegin(GL_LINES); { //White colour glColor3f(1.0f, 1.0f, 1.0f); //x, y, z //Vertex2f would be ideal, but doesn't appear (min view distance for perspective?) glVertex3f(-0.0001f, 0.0f, -0.01f); glVertex3f(0.0001f, 0.0f, -0.01f); } glEnd(); //Draw vertical crosshair glBegin(GL_LINES); { //Also white glColor3f(1.0f, 1.0f, 1.0f); //Again: x, y, z glVertex3f(0.0f, -0.0001f, -0.01f); glVertex3f(0.0f, 0.0001f, -0.01f); } glEnd(); //Rotate on the x axis (pitch) glRotatef(se::pl0.rX, 1.0f, 0.0f, 0.0f); //Rotate viewport on the y axis (yaw) glRotatef(se::pl0.rY, 0.0f, 1.0f, 0.0f); //Translate the world by the negative of our coordinates //Camera one way = objects the other... glTranslatef(-se::pl0.x, -se::pl0.y, -se::pl0.z); glCallList(1); //Show the screen we have been calculating, preparing the screen we were showing for drawing SDL_GL_SwapBuffers(); return; } void initDisplayLists(void) { glGenLists(1); cube block = cube(); glNewList(1, GL_COMPILE); { block.render(); } glEndList(); return; } </code></pre>
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