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I'm a software engineer, but not a game developer. I stumbled across DarkGDK, started playing with it, and now I'm working on my first game. I'm still learning the API, and have a couple questions.

Is there a function whereby I can pass a parameterized vector to determine if and where it intersects with my terrain? I'm using a height map and terrain texture, which works great. I'm applying my own physics engine to everything, including gun shots, and I don't want to have to render the bullet as an object just to test for collision. I'd rather compute continuous path and test for terrain intersection. Is there a function for this, or do I have to do this myself?

If I have to do this myself, can I get to the mathematical representation of the terrain? I assume its just a matrix, so I can test each square/triangle for intersection.

I came up with an algorithm to calculate intersection points of balistic trajectories on terrain. However, I need some information from the terrain matrix. I need at least the 4 corner points for each surface, assuming their all coplanar. It would be nice if I didn't have to calculate the normal vector either.

Hi,

Check out dbIntersectObject() under the "Basic3D" section in the help file. It's what you're looking for.

That works better for the next algorithm, projectile collision with object. I'm not sure how to apply it to terrain. It appears to only return a distance between the object (I assume the object origin) and the point of intersection. I need to know the point, not distance to, the intersection. dbIntersectObject only returns a float. I need 3 floats (x,y,z).

I put together some equations and tested them in Excel, but I need the mathematical description of the terrain. Basically, it calculates a path due to gravity, air friction, and windage with position in respect to time. I can probably use the dbIntersectObject to determine which processing frame the projectile intersects, but my algorithm determines the exact position on the terrain where the impact occurs.

I assume the terrain is a 3d mesh of squares or triangles. My algorithm would iterate through each square or triangle and determine the impact point of the plane. To do this, I need either the equation of the plane, 1 point and the normal vector, or 3 points. Then it tests whether the impact point is within the bounded square or triangle, which requires all bounding points or lines (3 for triangle, 4 for square). Lastly, it returns the world coordinates of the impact point.

The problem is, I need access to the matrix. Does anybody know how to do this? It doesn't appear that DarkGDK is very object oriented.

Hi,

I think you overlooked what the dbIntersectObject() returns. Yes, it returns a distance but this distance is from a given point until the intersection. Because of this, to get the point of intersection you just take the point of origin and add the distance.

For example:

float fDistance = dbIntersectObject( terrainID, 10, 1000, 10, 10, -1000, 10 );

Now the intersection point is X,Y,Z of ( 10, 1000 - fDistance, 10 )

Something along those lines.


Edit: DarkGDK is an API and is not object-oriented at all. There are other threads on how to access the vertices of a terrain object (or make your own). Try searching for "vertexdata" or "vertex data" with terrain possibly as a keyword. I still believe that dbIntersectObject() is all you need for the problem you're trying to solve - no sense in making it more complex than it really is.