urgent problem with overlapping bitmaps in DirectX

Question

hi everyone. so i was able to study directX over the course of a week and have successfully put up moving sprite on a white background. everything's fine it even follows my mouse input (i can drag it around). but the problem is when it runs across a piece of text drawn on the lower left part of the screen (using drawtext) the entire program hangs. the problem also occurs when i try to paint a background via drawFast and then try to paint the sprite over it via drawFast as well. the program hangs. i assume it could be a problem with the overlapping bitmaps but i do not know how to remedy it. any tips? i'm short of time too a deadline on the graphics component of our projects is coming up soon.

deryk_2784 · Answer

hi there. apparently the problem is in the external loop run for AI purposes. is there any way to work around this? currently we have a gameLoop() function set to do something like this: public void gameLoop() { while(target.Created) //this loop tells AI agents what to do and also modifies their corresponding bitmaps //to show what the agents are doing (i.e. a punch command is graphically represented //as a punch via bitmaps for(int nCtr=0; nCtr<alIA.Count;nCtr++) { ((TeamReactive)alIA[nCtr]).performAction(); } //this for loop simply draws the sprites contained in an array to reflect changes that //took place in the previous loop for(int i=0;i<csSprites.Length;i++) { csSprites[i].DrawNext(); } //this flips the back buffer to the front after all the sprites have drawn to the back buffer graphics.front.Flip(graphics.back FlipFlags.Wait); } the DrawNext() method of my Sprite object is now simply: public void DrawNext() { //some code here graphics.back.DrawFast(nXLocation nYLocation BitmapHolder frames[nCurrentFrame] DrawFastFlags.SourceColorKey | DrawFastFlags.DoNotWait); //more code here } now if i initialize 1 or 2 agents thus creating 1 or 2 bitmaps respectively everything runs at a fine pace. but if i create 3 or more agents the animations get really choppy. how do i know the first for loop(for the AI) is the problem? i took it out and ran the program. everything moved extremely well although the sprites couldn't be moved of course because of the lack of the pathplanning algorithm processed by the first for loop. is there any way to work around this? i've tried turning the first for loop into a thread but then the problem becomes the proper movement from one point to another. basically what happens is that when i click for a sprite to go to a certain point it just appears there. it doesn't go through the motion of going there which is something that happened with the AI loop in its original location. i'd appreciate any suggestions this is hurting our progress pretty badly.

Mykonine · Answer

Interesting. I've actually also had that same problem. I personally don't know what the problem is. Copy-pasting the code did the trick for me.

deryk_2784 · Answer

hi. fixed some of the problems. can now display multiples sprites with ease :) thanks. but now i've got another problem. i draw a background image behind the sprites but when i do the program slows down A LOT to the point that it takes around 1 second for the sprites to respond to a mouse click. aside from that the animations have become very choppy. before i added a background everything was running perfectly. but when i drew a background behind everything the program slowed down. could it be my pc? i use a p3 650Mhz with 256MB of RAM. if it's not my pc what could it be?

Mykonine · Answer

Does that problem have anything to do with the sprites overlapping? From the sounds of it the sprite right before the flip is the only thing showing up. Try sprite1.drawNext(); graphics.front.Flip(graphics.back FlipFlags.DoNotWait); Then try sprite2.drawNext(); graphics.front.Flip(graphics.back FlipFlags.DoNotWait); If both show only their corresponding sprite then your problem in sprite1.drawNext(); sprite2.drawNext(); graphics.front.Flip(graphics.back FlipFlags.DoNotWait); is probably due to overlapping sprites.

deryk_2784 · Answer

oops nevermind.. just figured that sizing thing out. :)

deryk_2784 · Answer

you also mentioned creating a surface with a specified size. how is this possible? i looked through the Surface class constructors and there seems to be no variation for allowing the assignment of a specific size of surface.

deryk_2784 · Answer

You should let the game loop do the flipping instead of having the drawNext methods flipping surfaces after every successive drawing i tried this earlier. a segment of my game loop goes something like... while(target.created) { //code sprite1.drawNext(); sprite2.drawNext(); graphics.front.Flip(graphics.back FlipFlags.DoNotWait); //more code } what happens is that only the second sprite gets drawn onto the screen. in the same way if i put the flip command between the two drawNext commands only the first one is drawn.

Mykonine · Answer

There are two overloads for the Surface.DrawFast method: public Void DrawFast (Int32 Int32 Surface DrawFastFlags) public Void DrawFast (Int32 Int32 Surface Rectangle DrawFastFlags) You are familiar with the first one because most likely that's what you're using. The second one adds a little extra functionality: instead of blitting the whole thing it blits only what's inside the rectangle onto the target surface. So here's the concept: Say I wanted a resolution of 800x600 on the screen. I had these surfaces that were 200 pixels wide and tall and since drawing off the edge of the surface causes bad errors it would just be better if I could clip it. So here's what I do: I create a surface sort of like a third buffer of size 1200x1000 (a 200 pixel margin on all sides). When I draw I draw onto that surface. Once the drawing routine is complete I use the second DrawFast to blit an 800x600 rectangle out of the middle of that third buffer onto the back buffer then flip. The result: Every pixel outside that 800x600 window is automatically clipped and you are saved to some extent from the problems of trying to blit a pixel to a coordinate that isn't on the screen. Something I recommend is to make a GraphicsHandler a wrapper for DirectDraw's main functionality. I use one that mainains the device back buffer front surface parent control and clipper. When I need to draw I blit it onto the surface provided by the GraphicsHandler.BackBuffer property. When I want to flip I call the GraphicsHandler.FlipSurfaces property. That way you are ensured that the flipping is not causing your flickering problems. I would double-check your animation classes. I looked through and found this: public void drawNext() { //...various lines of code graphics.back.DrawFast(xLocation yLocation BitmapHolder frame DrawFast.DoNotWait); //... various lines of code graphics.front.Flip(graphics.back FlipFlags.DoNotWait); } Every time you are calling drawNext you flip the surfaces. That's the reason for your flickering problems. You should only flip the surfaces after all the drawing routines are complete. In other words it should be: public void drawNext() { //...various lines of code graphics.back.DrawFast(xLocation yLocation BitmapHolder frame DrawFast.DoNotWait); //... various lines of code } You should let the game loop do the flipping instead of having the drawNext methods flipping surfaces after every successive drawing

deryk_2784 · Answer

...trying to blit a larger source bitmap onto a smaller target bitmap... how is this possible? i'm not sure how it happens if ever it does since the bitmap object to which i assign the actual file does not have any parameters for size. with regard to your technique of blitting to a larger surface then taking a clipping of that to blit to the back buffer could you elaborate more on how to do this? how do you clip the larger surface and draw it on to the back buffer? sorry i'm a relative newbie to directx. :) as for the drawNext method it goes something like this: public void drawNext() { //...various lines of code graphics.back.DrawFast(xLocation yLocation BitmapHolder frame DrawFast.DoNotWait); //... various lines of code graphics.front.Flip(graphics.back FlipFlags.DoNotWait); } it goes something like that where BitmapHolder is the surface to which the bitmap object is assigned and frame is the rectangle whose declaration is something like: frame = new Rectangle(new Point(00) new Size(800 121)); in this case i want the rectangle to contain everything from the upper left corner of the bitmap up to a width of 800 (the actual bitmap width) and height of 121 (the actual bitmap height).

Mykonine · Answer

The InvalidRectangleException was probably caused by trying to blit a larger source bitmap onto a smaller target bitmap. There are other exceptions but mostly in the vein of the rectangle bounds not being valid for the surface or operation performed. (Like index out of bounds exceptions) A common technique I've used is in fact not to blit straight onto the back buffer but to blit onto a surface that's larger than the actual screen surface then blitting a clipping from the larger surface to the actual back buffer before flipping. The flicker in your animation I'm guessing has to do with your sprite class not DirectX. What does the drawNext method do (in specifics)?

deryk_2784 · Answer

here's one more for you. sorry to keep the questions coming deadline's approaching. :) what causes an InvalidRectangleException? remember when i created two instances of the sprite and said they flicker? well i tried using a another image in place of the second sprite (i simply changed the resource name in the constructor so the object calls up a different file name) with only one frame of animation (i set that to 1 in the constructor too). problem is now the program brings up an Invalid RectangleException error when i run it. the weird thing is that it's exactly the same save for the different filename and number of frames. for the rectangle of course i set its dimensions to the dimensions of the new image and its Point setting to 00 so it starts at the upper left hand corner of the image. when i revert back to the old file set the number of frames to 4 and set the rectangle dimensions to match it the program works fine. help.... thanks :)

deryk_2784 · Answer

on an additional note the bitmaps seem to be alternating between refreshes. since i used two separate instances of the same animation i tried putting the two sprites (which are flickering) directly on top of one another. to my surprise the flicker disappeared and the two previously flickering objects looked as if they were one single smooth animation. however when i dragged one sprite off the top of the other they were back to flickering again. hope that helps you guys think of a way to solve this.

deryk_2784 · Answer

as you suggested in a previous thread of mine DirectDraw :)

Mykonine · Answer

Which API are you using DirectDraw or Direct3D?

deryk_2784 · Answer

well i can actually overlap animated sprites now. problem is they flicker when there are more than one of them onscreen. with just one aniamted sprite there is no flicker. i thought this had something to do with the graphics.front.flip() method so i took it out and typed it after the draw method of the second bitmap like this: bitmap1.drawNext(); bitmap2.drawNext(); graphics.front.Flip(graphics.back FlipFlags.Wait); the Flip() command used to be in each bitmap object's drawNext() method. when i placed it under the two statements as shown above i lost the flicker but only the second bitmap displayed. when i placed it in each bitmap object's drawNext() method they both displayed but with extensive flicker. any solutions?