Search Results

Search found 1 results on 1 pages for 'magnum39'.

Page 1/1 | 1 

  • iPhone OpenGL scrolling background jumps when texture is drawn for first time

    - by Magnum39
    I have been fighting a problem for a while now and would appreciate any help anybody could give. I have a sprite that moves within a landscape. The sprite remains in the center of the screen and the background moves to simulate that the sprite is moving within the landscape. I have split the landscape into sections so that I only draw the sections of the landscape that I need (are on screen). The Problem: As a new texture section of the screen appears on the screen (is drawn for the first time) the movement jumps. Almost like a frame is missed. I have done some timing experiments and I do not thinks a frame is missed. My processing is well below the 30fps that I have the animation set to. It only happens the first time the texture section is drawn. Is there something extra that is done the first time a texture is drawn? Here is the code: - (void) render{ // Sets up an array of values to use as the sprite vertices. const GLfloat sVerts[] = { -1.6f, -1.6f, 1.6f, -1.6f, -1.6f, 1.6f, 1.6f, 1.6f, }; static const GLfloat sTexCoords[] = { 0.0, 1.0, 1.0, 1.0, 0.0, 0.0, 1.0, 0.0 }; glDisableClientState(GL_COLOR_ARRAY); glEnableClientState(GL_VERTEX_ARRAY); glEnableClientState(GL_TEXTURE_COORD_ARRAY); // Setup opengl to draw the object in correct orientation, size, position, etc glLoadIdentity(); // Enable use of the texture glEnable(GL_TEXTURE_2D); glVertexPointer(2, GL_FLOAT, 0, sVerts); glTexCoordPointer(2, GL_FLOAT, 0, sTexCoords); // draw the texture // set the position of the first tile float xOffset = -4.8; float yOffset = 4.8; int i; int y; int currentTexture = textureA; for(i=0; i<2; i++) { for(y=0; y<2; y++) { // test for the texture tile on the screen if not on screen then do not draw float localX = xOffset+(3.21*y); float localY = yOffset-(3.21*i); float xDiff = monkeyX - localX; float yDiff = monkeyY - localY; if(((xDiff < 3.2) && (xDiff > -3.2)) && ((yDiff <2.7) && (yDiff > -2.7))) { // bind the texture and set the vertex data pointers glBindTexture(GL_TEXTURE_2D, spriteTexture[currentTexture]); // move to draw position for the texture glLoadIdentity(); glTranslatef((localX+self.positionX), (localY+self.positionY), 0.0); //draw the texture glDrawArrays(GL_TRIANGLE_STRIP, 0, 4); } currentTexture++; } } }

    Read the article

1