heat distortion and rendering order


I’m trying to do heat distortion effect in ps2. (well, i guess this is not really relavant to opengl, but i want to ask this anyway) I have an actual distortion effect going on the screen. (it’s in 3D world space, so i’m using a grid placed in the game world) But, the problem is that it distorts an object between a camera and the grid. So, when i distorts uv coordinate on the grid, it also distorts the image of this object. The result is that i can see the boundary of the object distorting on the screen. … I know that i can fix this if i render from back to front … but in the given state, it’s not easy to do it. (not to mention that it would be expensive operation.)

Is there any way to fix this? I think this kind of problem also arises for opengl or directx when you want to do heat distortion in 3D world. I know that there are ppl out there who did heat distortion effect in the past … pleeze help!