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# Help! Please take a look at this code...

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Hey! I''m very close to making my first tile engine from scratch (with a little help from trick of thewindows programming gurus) My problem is that I get strange graphic anomalies when I scroll the screen around... here is my draw map function: void DrawWorld(void) { int index, index_x, index_y; // looping vars int start_map_x,start_map_y, // map positions end_map_x,end_map_y; int offset_x, offset_y; // pixel offsets within cell // clear the drawing surface // DDraw_Fill_Surface(lpddsback, 0); // check for movement (scrolling) if (KEYDOWN(VK_RIGHT)) { if ((world_x+=4) >= 1280) world_x = 1279; } // end if else if (KEYDOWN(VK_LEFT)) { if ((world_x-=4) < 0) world_x = 0; } // end if if (KEYDOWN(VK_UP)) { if ((world_y-=4) < 0) world_y = 0; } // end if else if (KEYDOWN(VK_DOWN)) { if ((world_y+=4) >= 896) world_y = 895; } // end if // compute starting map indices by dividing position by size of cell start_map_x = world_x/64; // use >> 6 for speed, but this is clearer start_map_y = world_y/64; // compute end of map rectangle for best cast i.e. aligned on 64x64 boundary end_map_x = start_map_x + 10 - 1; end_map_y = start_map_y + 7 - 1; // now compute number of pixels in x,y we are within the tile, i.e // how much is scrolled off the edge? offset_x = -(world_x % 64); offset_y = -(world_y % 64); // adjust end_map_x,y for offsets if (offset_x) end_map_x++; if (offset_y) end_map_y++; // set starting position of first upper lh texture int texture_x = offset_x; int texture_y = offset_y; // draw the current window for (index_y = start_map_y; index_y <= end_map_y; index_y++) { for (index_x = start_map_x; index_x <= end_map_x; index_x++) { // set position to blit // textures.x = texture_x; // textures.y = texture_y; // set frame currentFrame = world[index_y][index_x] - ''0''; // draw the texture rcRect.left = currentFrame % 10 * 64; rcRect.top = currentFrame / 10 * 64; rcRect.right = currentFrame % 10 * 64 + 64; rcRect.bottom = currentFrame / 10 * 64 + 64; hRet = g_pDDSBack->BltFast(texture_x, texture_y, g_pDDSOne, &rcRect, DDBLTFAST_NOCOLORKEY); // update texture position texture_x+=64; } // end for map_x // reset x postion, update y texture_x = offset_x; texture_y += 64; } // end for map_y // draw some info Draw_Text_GDI("USE ARROW KEYS TO MOVE, to Exit.",8,8,RGB(255,255,255),g_pDDSBack); sprintf(buffer,"World Position = [%d, %d] ", world_x, world_y); Draw_Text_GDI(buffer,8,480 - 32 - 24,RGB(0,255,0),g_pDDSBack); // flip the surfaces hRet = g_pDDSPrimary->Flip(NULL, 0); } The graphic anamolies include rapid flashing around the right hand side of the screen and the bottom, as well as tiles getting "stuck" on the side of the screen and scrolling around with user for a bit... if anyone has any ideas then PLEASE HELP! Thanks... -Jesse Sorry to be bugging this forum so much but I went in over my head when I decided to make a directdraw tile engine for my first project... but I''ve almost got it. Thanks for everyone''s help!

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