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Asked: 2026-05-11T01:34:13+00:00

I called this function once per frame and it took my FPS from >400

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I called this function once per frame and it took my FPS from >400 to 33. Why?

sw blt(const PtRect *dstRect, Texture *src, const PtRect *srcRect, RenderDevice::bltFlags flags=RenderDevice::bltDefault) {     assert(src);     GL_Texture *glsrc = dynamic_cast<GL_Texture*>(src);     if (glsrc == 0)         return -1;      PtRect srcRect2(0, 0, src->width, src->height);     if (srcRect == 0)         srcRect = &srcRect2;      PtRect dstRect2(0, 0, srcRect->makeWidth(), srcRect->makeHeight());     if (dstRect == 0)         dstRect = &dstRect2;      glColor4f(1.0f, 1.0f, 1.0f, 1.0f);      glEnable(GL_TEXTURE_2D);     glBindTexture(GL_TEXTURE_2D, *glsrc->getTex());      glBegin( GL_QUADS );     glNormal3f( 0.0f, 0.0f, 1.0f );     for (size_t i=0; i<350; i++)     {         glTexCoord2f( srcRect->left /src->width, srcRect->top/src->height);    glVertex2f(dstRect->left,  dstRect->top);         glTexCoord2f( srcRect->right/src->width, srcRect->top/src->height);    glVertex2f(dstRect->right, dstRect->top);         glTexCoord2f( srcRect->right/src->width, srcRect->bottom/src->height); glVertex2f(dstRect->right, dstRect->bottom);         glTexCoord2f( srcRect->left /src->width, srcRect->bottom/src->height); glVertex2f(dstRect->left,  dstRect->bottom);     }     glEnd();     return 0; }
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1 Answer

  1. For performance you should load your textures in an init function and use a list to display then later on the main render function, for example:

    // Generate texture object ID glGenTextures(1, img); glBindTexture(GL_TEXTURE_2D, img);  // Set Texture mapping parameters glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S, GL_REPEAT); glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T, GL_REPEAT); glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER, GL_LINEAR);  LoadBMP('texture.bmp');

    Then on the main render function you have something like:

    // Front face of Cube glBindTexture(GL_TEXTURE_2D, img); glBegin(GL_QUADS); glTexCoord2f(0.0f, 0.0f); glVertex3f(-fSize, fSize, fSize); glTexCoord2f(0.0f, 1.0f); glVertex3f(-fSize, -fSize, fSize); glTexCoord2f(1.0f, 1.0f); glVertex3f(fSize,-fSize, fSize); glTexCoord2f(1.0f, 0.0f); glVertex3f(fSize,fSize, fSize); glEnd();

    As you can see you can wrap the texture on the parameters instead of repeating it over and over in a loop.

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