Posted: 1/2/2016 9:09 AM
Post subject: Overhead display for 3D games
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jlun2
Skilled player (1707)
Joined: 9/17/2009
Posts: 4952
Location: ̶C̶a̶n̶a̶d̶a̶ "Kanatah"
GBA TASer of 2010
First, I don't mean 3D display; I meant games like SM64. I've been trying to make a lua script to display enemy data over them as they appear just like how people do so for 2D games, and I can't seem to figure out how to convert their x,y,z coordinates into x,y screen coordinates. How do I approach this? I tried taking account with the player's camera angle, but there seems to be lots of cases if I do. Any general method to do this?
LLCoolDave wrote:
This seems to be competing for the "Worst looking TAS of 2011" Award.
Posted: 1/2/2016 6:52 PM
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Warp
Banned User, Former player
Joined: 3/10/2004
Posts: 7698
Location: Finland
The rendering engine itself obviously transforms and projects all triangles onto the screen in order to render them. I don't know if the N64 does this in software or hardware. Is it possible to access these transformed&projected coordinates from the emulator using lua script? That would be an easy solution. If it's not possible, and you only have access to the enemy model 3D world coordinates and the camera parameters, you'll have to do the transformation&projection yourself. It's difficult to give a concrete answer in code without knowing exactly what camera parameters are available. You'll probably have to give more detail about this. But in general, for each point you want to project, you need to convert that point from world coordinates to camera coordinates (there are several possible ways of doing this, one of them is using a transformation matrix, which might even be directly in the camera data, depending on how the rendering engine works) and then project it to the screen (again, there are a couple of ways of doing this, one of them also being a transformation matrix, which might be in the camera data itself.) Essentially you would be doing a few point-matrix multiplications. What those matrices are exactly, it depends on how the camera parameters are defined in the game. (Edit: Oh, and I forgot that there are a few more steps you need to do in order to clip coordinates that are behind the camera, else they would be mirrored in front of it. But this is relatively easy to do.)