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# Terrain Collisions

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I have created a simply program that loads a terrain from a bitmap file and I can't seem to get the collision detection correct. I'm currently simply getting the triangle on which the camera lies, creating a plane from the three points, and plugging in X and Z values. Anyone know while this method's not working? Here's my project and code. [edited by - ms291052 on September 23, 2003 6:31:55 PM]

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1. It is a heightmap terrain with all points over 2D grid just with different height
2. You already know the triangle you are standing over, because you know X and Z coordinate
3. You now need to find out the Y coordinate over the terrain, therefore itd be best if you could draw the whole situation on a paper and try to find out. This is how I solved same problem - after you draw it on a paper (from 2 different angles), youll immediately see it.

4. Of course, you can still count intersections with plane

Avenger game

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The method I'm going to suggest might only work for terrains.

I assume that you are trying to setup a terrain on the x-z plain and therefore the y-component gives you the height.

I assume you have a terrain generation function that gives you the height component at a specified location like

GetHeight (x, z) ;

The function could be reading this from a height map, or using some perlin noise stuff, lets say.

All you have to do now is to check your viewpoints y component with the height at a particular location on the terrain. For example, suppose you are at location (x, y, z). You could check for collisions like

if (y < GetHeight (x, z)) {
// ... went below the terrain, get back
y = GetHeight (x, z) ;

HandleCollisionWithTerrain () ;
}

This should work.

[edited by - UdayK on September 24, 2003 2:37:02 AM]

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The problem with that is what happens when you start appying matricies to the heightmap. That''s the reason why it doesn''t seem to work with mine. How do you apply a matrix to a specific point?

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D3DXVec3Transform for D3DXVECTOR3