Develop Reference

why is my marching cubes algorithm so slow?

i have somewhat implemented marching cubes in unity/c# (you dont need to know unity to help me though) and i cant stop feeling like i have made a big mistake in my code because it is so slow. i am already running it on a separate thread but it just takes ages to complete. please help me optimize my code.
private void _UpdateChunk()
{
lock (this)
{
// clear the tri, vert and uv lists
ClearMeshData();
// Loop through each "cube" in the terrain.
for (int x = 0; x < width; x++)
{
for (int y = 0; y < height; y++)
{
for (int z = 0; z < width; z++)
{
// Create an array of floats representing each corner of a cube and get the value from our terrainMap.
float[] cube = new float[8];
float[] strengths = new float[8];
for (int i = 0; i < 8; i++)
{
Vector3Int corner = new Vector3Int(x, y, z) + gamedata.CornerTable[i];
cube[i] = terrainMap[corner.x, corner.y, corner.z].BlockType;
strengths[i] = terrainMap[corner.x, corner.y, corner.z].Strength;
}
// Pass the value into the MarchCube function.
MarchCube(new Vector3(x, y, z), cube, strengths);
}
}
}
}
}
void MarchCube(Vector3 position, float[] cube, float[] strengths)
{
// Get the configuration index of this cube.
int configIndex = GetCubeConfiguration(cube);
// If the configuration of this cube is 0 or 255 (completely inside the terrain or completely outside of it) we don't need to do anything.
if (configIndex == 0 || configIndex == 255)
return;
// Loop through the triangles. There are never more than 5 triangles to a cube and only three vertices to a triangle.
int edgeIndex = 0;
Vector3 vert1 = new Vector3();
Vector3 vert2 = new Vector3();
float vert1sample = 0;
float vert2sample = 0;
float lerp = 0;
int indice = 0;
for (int i = 0; i < 5; i++)
{
for (int p = 0; p < 3; p++)
{
// Get the current indice. We increment triangleIndex through each loop.
indice = gamedata.TriangleTable[configIndex, edgeIndex];
// If the current edgeIndex is -1, there are no more indices and we can exit the function.
if (indice == -1)
return;
// Get the vertices for the start and end of this edge.
vert1 = position + gamedata.EdgeTable[indice, 0];
vert2 = position + gamedata.EdgeTable[indice, 1];
vert1sample = strengths[gamedata.EdgeIndexTable[indice, 0]];
vert2sample = strengths[gamedata.EdgeIndexTable[indice, 1]];
// Get the midpoint of this edge.
lerp = Mathf.Abs(vert1sample) / (Mathf.Abs(vert2sample) + Mathf.Abs(vert1sample));
Vector3 vertPosition = Vector3.Lerp(vert1, vert2, lerp);
// Add to our vertices and triangles list and incremement the edgeIndex.
vertices.Add(vertPosition);
triangles.Add(vertices.Count - 1);
if (getChunkVoxel(vert1 + chunkPosition) != 0)
{
uvs.Add(new Vector2(getChunkVoxel(vert1 + chunkPosition) - 1, 0));
}
else
{
uvs.Add(new Vector2(getChunkVoxel(vert2 + chunkPosition) - 1, getChunkVoxel(vert2 + chunkPosition) - 1));
}
edgeIndex++;
}
}
}
int GetCubeConfiguration(float[] cube)
{
// Starting with a configuration of zero, loop through each point in the cube and check if it is below the terrain surface.
int configurationIndex = 0;
for (int i = 0; i < 8; i++)
{
// If it is, use bit-magic to the set the corresponding bit to 1. So if only the 3rd point in the cube was below
// the surface, the bit would look like 00100000, which represents the integer value 32.
if (cube[i] < terrainSurface)
configurationIndex |= 1 << i;
}
return configurationIndex;
}
it appears that this is the part that slows my game down, help would be appreciated
i already made it faster by changing terrainpoint from a class to a struct but it is still very slow.

One main reason it is slow is that there is a lot of allocations in the loop putting a lot of pressure on the garbadge collector. There is currently 11 allocation per "cube" in the terrain in _UpdateChunk and up to 17 in MarchCube (possibly even more if the expressions like position + gamedata.EdgeTable[indice, 0] allocates a new vector). This is not reasonable. Many allocation are not needed. For example cube and strengths can be preallocated once for all the cubes in the beginning of _UpdateChunk. You do not need to allocate the vector in the expression to compute corner: you can just compute the components separately manually (or you can possibly preallocate the vector and reset its component when needed). The same thing applies for the new Vector3(x, y, z) can can be preallocated and set in the loop. Such an algorithm is computationally intensive so you should get away any overhead like virtual method calls and allocations/GC -- only low-level arrays accesses and mathematical operations should remains.
Note that some computations can be optimized. For example GetCubeConfiguration can be modified so to be branchless. Mathf.Abs(vert1sample) can be precomputed so not to compute it twice (though the compiler may already do that). I am also wondering if the expression like vertices.Add are efficient but this is dependent of the type of container which is not provided here.

Using perlin noise field, to get random positions for objects to spawn

I am trying to make a system that uses a perlin noise field to generate random positions that are then saved, or saved as the are generated, to a list. Then using that list the game will use those positions to spawn in objects within the level. I think that I might be on the right track, but I might have a few things in the wrong places.
Here is a link to an image of all the things that I think are relevant:
the blue dots should be the saved locations that are added to the list. But i am only getting one position 5 times, which is the correct number of positions but they are all the same position that is the problem.
// --- Random Generation of Objects --- //
Color[] colourMap = new Color[mapWidth * mapHeight];
for(int y = 0; y < mapHeight; y++) {
for(int x = 0; x < mapWidth; x++) {
float currentHeight = noiseMap[x, y];
for(int i = 0; i < regions.Length; i++) {
// --- Random Gen of Asteroids --- //
if(currentHeight <= regions[i].height) {
colourMap[y * mapWidth + x] = regions[i].colour;
Vector3 ping = new Vector3(x, 0, y);
asteroids.Add(ping);
Debug.Log(asteroids[i]);
break;
}
}
}
}
Anyway thank you for the help and reading this far, please let me know if you need anything more.

Tile Engine Collision Optimization

Alright, so today I decided to try to further optimize my collision detection code for my tile engine.
This is what I did:
Circle class checks if there are points within range. If there are, then check for collision between player and tile.
Code:
int tileWidth = 128;
int tileHeight = 128;
int[,] Layer3 = { 1, 1, 1, etc... };
int tileMapWidth = Layer3.GetLength(1);
int tileMapHeight = Layer3.GetLength(0);
Rectangle tile, tile2;
for (int x = 0; x < tileMapWidth; x++)
{
for (int y = 0; y < tileMapHeight; y++)
{
int wallIndex = Layer3[y, x];
if (wallIndex == 1) //Full-sized Tile Collision (128 x 128)
{
if (collisionCircle.Contains(new Vector2(x * tileWidth + (tileWidth / 2) + (int)Player.camera.Position.X,
y * tileHeight + (tileHeight / 2) + (int)Player.camera.Position.Y))) //+ tile / 2 is for centering the point
{
tile = new Rectangle(x * tileWidth + (int)Player.camera.Position.X, y * tileHeight + (int)Player.camera.Position.Y, tileWidth, tileHeight);
Collide(tile);
}
}
}
}
This would check throughout layer3 if there is a "1". If there is, assign rectangle and check for collision if point is inside collision radius.
Also, I checked this code(with a draw method), and I know it's working properly, at least the behavior.
I added in about 120,000(32 x 3888) tiles to try to make it lag, and before the code, it lagged a little bit. But after I added in the code, it lagged even more so.
I thought that since it would only check for collision between tiles(points) that are within the radius it wouldn't even remotely lag, but that's not the case...
Any help/ideas on how to optimize this would be great.
Thanks a lot,
Shyy
EDIT:
Cirlce.Contains() code:
public bool Contains(Vector2 Point)
{
return ((Point - position).Length() <= radius);
}
I used a circle because I've heard it's faster than using a rectangle.

Another possible optimization is instead of
return ((Point - position).Length() <= radius);
use
return ((Point - position).LengthSquared() <= radius * radius);
This is faster because Vector2.Length() has to perform a costly square root operation. Vector2.LengthSquared() does not have to perform that slow operation. The radius has to be multiplied by itself to account for the length from the vector being squared.
It sounds like you're trying to determine what tiles you don't need to use for collision with the player. Another optimization you could do is that if a tile at (X=5,Y=5) is above and to the left of the player, then you don't need to check a tile at (X=4,Y=4). Similarly if (X=5,Y=5) is below and to the right, (X=6,Y=6) is guaranteed to be too far as well. Try to determine when you've passed the player and no longer need to check collisions.

I suggest to loop only over visible tiles in screen to check collision using movement offset.
i will try something from my head..
for x as integer = 0 + offSetX to tilesInWidth + offSetX
for y as integer = 0 + offSetY to tilesInHeight + offSetY
if player.insideCircle(player.position, radius) '
object = layer(y,x);
if player.collideWith(object) then Collide()
end if
next
next

Why my Images flickers in my xna project?

I have some problems on the display of my model with texture.
Everything works perfectly, however, I use a loop to repeat the texture to represent a floor 20 X 20 on the screen. My texture is repeated correctly. But I do not understand why all my textures generate a flicker ...
I noticed that images are superimposed on each other. I'm sure I checked my loop is coded correctly.
see screenshot:
my code (loop function generation ground):
//Function draw - ground land
private void draw_groundLand(Vector3 position_model_origin)
{
//example generation mode 4x4 cubes
int[,,] MatriceWorldCube = new int[1,2,2];
MatriceWorldCube[0, 0, 0] = 1;
MatriceWorldCube[0, 0, 1] = 1;
MatriceWorldCube[0, 1, 0] = 2;
MatriceWorldCube[0, 1, 1] = 1;
int height = MatriceWorldCube.GetLength(0);
int width = MatriceWorldCube.GetLength(1);
int length = MatriceWorldCube.GetLength(2);
Vector3 pos_reference = position_model_origin;
for (int thickness = 0; thickness < height; thickness ++)
{
for (int column = 0; column < width; column ++)
{
for (int line = 0; line < length ; line ++)
{
// Copy any parent transforms.
Matrix[] transforms = new Matrix[model_ground_land1.Bones.Count];
model_ground_land1.CopyAbsoluteBoneTransformsTo(transforms);
// Draw the model. A model can have multiple meshes, so loop.
foreach (ModelMesh mesh in model_ground_land1.Meshes)
{
// This is where the mesh orientation is set, as well
// as our camera and projection.
foreach (BasicEffect effect in mesh.Effects)
{
effect.EnableDefaultLighting();
effect.World = transforms[mesh.ParentBone.Index] *
Matrix.CreateRotationY(cubeGroundLand1_modelRotation) * Matrix.CreateTranslation(position_model_origin);
effect.View = View;
effect.Projection = Projection;
}
// Draw the mesh, using the effects set above.
mesh.Draw();
}
position_model_origin.X = (float)(line +1);
}
position_model_origin.X = pos_reference.X;
position_model_origin.Z = (float)(column +1);
}
position_model_origin.Z = pos_reference.Z;
position_model_origin.Y = (float)(thickness+1);
}
position_model_origin.Y = pos_reference.Y;
position_model_origin = pos_reference;
}
Thank you in advance for your help. I lose patience (over a whole weekend ^ ^)

It's Z-fighting. Z-buffer precision falling with distance so far objects have more "flickers" GPU can't figure out which polygon is on top because tail of the z-buffer value isn't precise enough to distinguish 2 almost equal values.
You have 6 ways to fix it:
Move geometry or do not display part that is below.
Use something like polygon offset in OpenGL
Use CPU z-sorting instead of z-buffer.
Use only one object with 2 textures instead of 2 objects + some shaders (i don't know what exactly you are trying to achieve)
Use larger z-buffer.
Move clip planes closer to each other it will increase precision.

Generating terrain in C# using perlin noise

I'm working on civilization game in C# and XNA. I use a two dimensional integer array, populated with a loop, to generate tiles, I've done a ton research and have been unable to find a way to generate earth like terrain. Can anyone explain how to do this or at least give me code that could do it, though I would prefer and explanation? Thank you.

I use an algorithm similar to this to make my terrain. Basicly it generates some random numbers and uses a sine wave to generate hills, when combined they give a nice hilly landscape. Note that you can add a loop and array of values if you want more than just 3 passes.
private void GenerateTerrain()
{
terrainContour = new int[Width*Height];
//Make Random Numbers
double rand1 = randomizer.NextDouble() + 1;
double rand2 = randomizer.NextDouble() + 2;
double rand3 = randomizer.NextDouble() + 3;
//Variables, Play with these for unique results!
float peakheight = 20
float flatness = 50
int offset = 30;
//Generate basic terrain sine
for (int x = 0; x < Width; x++)
{
double height = peakheight / rand1 * Math.Sin((float)x / flatness * rand1 + rand1);
height += peakheight / rand2 * Math.Sin((float)x / flatness * rand2 + rand2);
height += peakheight / rand3 * Math.Sin((float)x / flatness * rand3 + rand3);
height += offset;
terrainContour[x] = (int)height;
}
}
Then to fill the heightmap just loop through the values and check if it is above the threshold or not.
for (int x = 0; x < Width; x++)
{
for (int y = 0; y < Height; y++)
{
if (y > terrainContour[x])
tiles[x, y] = Solid Tile
else
tiles[x, y] = Blank Tile
}
}
Theres much more you can add to it, I've added more randomness and indenting some tiles by 1 up or down for better terrain. And adding more sine waves will make it more realistic.
Try using 2D Perlin Noise algorithms, and selecting certain heights to make caves and more advanced terrain, as this is now what I do, but this code here is a good start.