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I'm currently working on a Voxel game in 3D and need a tad bit of help to figure out what Voxel the player is looking at. This is the data I currently have:

GRRLIB_Camera3dSettings(Player.x, Player.y, Player.z + 4, 0,0,1, Player.x + Camera.lookx,Player.y + Camera.looky,Player.z + Camera.lookz);

And the two 3d arrays that contains the player cords and block cords:

struct Player{ int X; int Y; int Z; } int World[X_MAX][Y_MAX][Z_MAX]; //The cords are ALWAYS positive. ( and the array data: 0 Means air, anything higher is solid), The player

(GRRLIB camera is described here: http://grrlib.santo.fr/doc/group___all_func.html#ga7300940a38526ab5aa9be0f4abe4a32a)

So what I basically need to understand is how I would implement ray tracing using this data. The whole project can be found here: https://github.com/filfat/WiiCraft

For clarification I am asking for a simple way in C or C++ to create a Ray tracing algorithm that would be used in a Minecraft like game for selecting the block the player is looking at, all data that is needed is above. So in short I need help to understand the math in a Ray Tracing algorithm and need a simple example so I could implement it myself.

Thanks! :)

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  • \$\begingroup\$ Please describe a bit more what you've tried and exactly what the problem is you're having now. How to implement an entire feature is a bit broad, so I'd suggest narrowing the scope if that's your question. \$\endgroup\$ Commented Nov 10, 2014 at 15:55
  • \$\begingroup\$ Alright, edited question to be more understandable. \$\endgroup\$ Commented Nov 10, 2014 at 19:13
  • \$\begingroup\$ this is called traversing. It is the most important and basic setup step before the actual ray/thing collision routine takes place, to reduce the potential collider's set. Some people uses marching as a specific case of traversal, which incrementally progresses in the partitionning structure, often using crazy SSE tricks for packet marching, when the structure is regular enough (grids..). \$\endgroup\$ Commented Nov 11, 2014 at 1:44
  • \$\begingroup\$ @v.oddou Didnt not know that, thanks for the heads up :) \$\endgroup\$ Commented Nov 11, 2014 at 6:17
  • \$\begingroup\$ People coming here from search engine, see also: Cast ray to select block in voxel game. \$\endgroup\$ Commented Feb 20, 2021 at 21:39

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I assume your world is represented as a grid, the algorithm you need to do line grid intersection is called Digital differential analyzer algorithm. The code too much to write quickly, you can find a full explanation here.

This algorithm/technique is used to solve different problems that need interpolating a variable over an interval. It's similar to Bresenham line drawing algorithm but extended into 3D Grid.

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