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SDL/openGL Texturing Problem


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#1 Darir   Members   -  Reputation: 100

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Posted 07 January 2012 - 11:07 AM

I'm writing a program that needs to display a textured 32x32 square from a 32x32 section of a tilemap. I'm using sdl to divide up the tilesheet and then register each individual tile as a separate texture.The problem is that nothing renders at all. I've checked the code out a good number of times, so I was hoping someone else would spot the problem. Thanks.

struct Texture {
SDL_Surface* tex;
GLuint texHandle;
GLint colorNum;
GLenum format;
};
//class render holds a tilesheet and manages it
class renderer {
private:
short width, height;
SDL_Surface* tilesheet;
std::vector<Texture*> tile;]//null will render to the screen
SDL_Surface* destination;
SDL_Surface* loadOptimized(std::string filename);
bool divideTilesheet();
public:
//regular loaded constructor
renderer(std::string filename, SDL_Surface* udestination);
//for creating a renderer with a procedurally generated tilesheet
renderer(SDL_Surface* utilesheet, SDL_Surface* udestination);
//tilex and tiley are both zero-based, so the upper-left tile would be (0, 0)
void render(int tilex, int tiley, int locx, int locy);
[color=#282828][font=helvetica, arial, sans-serif]SDL_Surface* getResult() {return destination;}
};
renderer::renderer(std::string filename, SDL_Surface* udestination) {
tilesheet = loadOptimized(filename);
destination = udestination;
width = tilesheet->w/tileSize;
height = tilesheet->h/tileSize;
divideTilesheet();
}
renderer::renderer(SDL_Surface* utilesheet, SDL_Surface* udestination) {
tilesheet = utilesheet;
destination = udestination;
width = tilesheet->w/tileSize;
height = tilesheet->h/tileSize;
divideTilesheet();
}
bool renderer::divideTilesheet() {
//make sure we don't leave any previous tiles
tile.clear();
for(int y = 0; y < height; y++) {
  for(int x = 0; x < width; x++) {
   SDL_Surface* newTile = NULL;
   newTile = SDL_CreateRGBSurface(0, tileSize, tileSize, 32, 0, 0, 0, 0);
   SDL_Rect clip;
   clip.x = x*tileSize;
   clip.y = y*tileSize;
   clip.w = tileSize;
   clip.h = tileSize;
   SDL_Rect dest;
   dest.x = 0;
   dest.y = 0;
   SDL_BlitSurface(tilesheet, &clip, newTile, &dest);
   //the texture is created, so now we have to register it
   Texture* newTex = new Texture();
   newTex->tex = newTile;
   newTex->colorNum = newTex->tex->format->BytesPerPixel;
   if(newTex->colorNum == 4) {
		if(newTex->tex->format->Rmask == 0x000000ff)
		 newTex->format = GL_RGBA;
		else
		 newTex->format = GL_BGRA;
   }
   else if(newTex->colorNum == 3) {
		if(newTex->tex->format->Rmask == 0x000000ff)
		 newTex->format = GL_RGB;
		else
		 newTex->format = GL_BGR;
   }
   glGenTextures(1, &(newTex->texHandle));
   glBindTexture(GL_TEXTURE_2D, newTex->texHandle);
   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_WRAP_S, GL_CLAMP_TO_EDGE);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
   SDL_LockSurface(newTex->tex);
   glTexImage2D(GL_TEXTURE_2D, 0, newTex->colorNum, newTex->tex->w, newTex->tex->h, 0, newTex->format, GL_UNSIGNED_BYTE, newTex->tex->pixels);
   SDL_UnlockSurface(newTex->tex);

   tile.push_back(newTex);
  }
}
return true;
}
SDL_Surface* renderer::loadOptimized(std::string filename) {
SDL_Surface* loaded = NULL;
SDL_Surface* optimized = NULL;
loaded = SDL_LoadBMP(filename.c_str());
if(loaded != NULL) {
  optimized = SDL_DisplayFormat(loaded);
  SDL_FreeSurface(loaded);
}
else return NULL;
return optimized;
}
void renderer::render(int tilex, int tiley, int locx, int locy) {
if(destination) {
  SDL_Rect dest;
  dest.x = locx;
  dest.y = locy;
  SDL_BlitSurface(tile[tiley*width + tilex]->tex, NULL, destination, &dest);
}
else {
  //render to the screen with opengl
  glEnable(GL_TEXTURE_2D);
  glBindTexture(GL_TEXTURE_2D, tile[tiley*width + tilex]->texHandle);
  glBegin(GL_QUADS);[/font][/color]
  glColor4f(1.0, 1.0, 1.0, 1.0);

   glTexCoord2f(0, 0);
   glVertex2f(float(locx), float(locy));
   glTexCoord2f(1, 0);
   glVertex2f(float(locx + tileSize), float(locy));
   glTexCoord2f(1, 1);
   glVertex2f(float(locx + tileSize), float(locy + tileSize));
   glTexCoord2f(0, 1);
   glVertex2f(float(locx), float(locy + tileSize));
  glEnd();
  glDisable(GL_TEXTURE_2D);
}
}


I've tried using method, but that wasn't working, either; I removed it before I originally posted here. I even tried rendering a regular square without texturing just below the textured one in the code to make sure that it hadn't somehow been transformed out of the view of the screen. It rendered, but I still can't get the textured square to render at all. It won't render black, white, or any other color; I've changed the background color several times to make sure of that. I've also checked to make sure that every tile gets a texture handle and they do, which is making me think that the mistake is either with generating the tiles with SDL or with the rendering code.

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#2 MaxFire   Members   -  Reputation: 170

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Posted 30 January 2012 - 08:27 AM

Hey dude your texture might not be 2^n on both width and height. It could also be cause you have blank pixels in your new surface to test this useSDL_FillRect the whole surface just after surface creation ( fill with pixles with alpha of 0 ).

#3 V-man   Members   -  Reputation: 805

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Posted 30 January 2012 - 11:05 AM

Hey dude your texture might not be 2^n on both width and height. It could also be cause you have blank pixels in your new surface to test this useSDL_FillRect the whole surface just after surface creation ( fill with pixles with alpha of 0 ).


If you have GL 2 and above, you can make any texture (1D, 2D, 3D, cube) a non power of 2.
http://www.opengl.org/wiki/NPOT_Texture
Sig: http://glhlib.sourceforge.net
an open source GLU replacement library. Much more modern than GLU.
float matrix[16], inverse_matrix[16];
glhLoadIdentityf2(matrix);
glhTranslatef2(matrix, 0.0, 0.0, 5.0);
glhRotateAboutXf2(matrix, angleInRadians);
glhScalef2(matrix, 1.0, 1.0, -1.0);
glhQuickInvertMatrixf2(matrix, inverse_matrix);
glUniformMatrix4fv(uniformLocation1, 1, FALSE, matrix);
glUniformMatrix4fv(uniformLocation2, 1, FALSE, inverse_matrix);




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