游戏地形编辑器：世界坐标转纹理坐标的适配问题（Chunk与纹理尺寸不同）

Hey there! Let's break down how to solve this coordinate conversion problem—it's all about mapping the chunk's world space to the larger texture space with a simple scaling factor. Here's a step-by-step approach tailored to your setup:

Core Concept #

When your layer texture size is larger than the chunk size, you just need to calculate a scale ratio that maps each unit of chunk space to the corresponding number of texture pixels. For your case, that ratio is 128 / 32 = 4—meaning every 1 unit in the chunk translates to 4 pixels in the layer texture.

Step-by-Step Implementation #

1. Identify the Chunk Containing the Hit Point #

First, figure out which chunk your raycast hit belongs to. Assuming your terrain is laid out on the XZ plane:

const int ChunkSize = 32;
const int LayerTextureSize = 128;
Vector3 worldHitPos = YourRaycastHitResult.Position;

// Calculate chunk indices (floor to get the lower bound of the chunk)
int chunkX = Mathf.FloorToInt(worldHitPos.x / ChunkSize);
int chunkZ = Mathf.FloorToInt(worldHitPos.z / ChunkSize);

2. Convert to Chunk-Local Coordinates #

Next, translate the world position into coordinates relative to the chunk's origin (so values range from 0 to ChunkSize):

// Get the chunk's world origin
Vector3 chunkOrigin = new Vector3(chunkX * ChunkSize, 0, chunkZ * ChunkSize);

// Calculate local position within the chunk
float localX = worldHitPos.x - chunkOrigin.x;
float localZ = worldHitPos.z - chunkOrigin.z;

3. Scale to Texture Coordinates #

Apply the scale factor to map the local chunk coordinates to the larger texture space:

float scaleFactor = (float)LayerTextureSize / ChunkSize;

// Floating-point texture coordinates (great for smooth sampling)
float texCoordX = localX * scaleFactor;
float texCoordZ = localZ * scaleFactor;

// If you need integer pixel indices (for direct pixel drawing)
int texPixelX = Mathf.Clamp(Mathf.RoundToInt(texCoordX), 0, LayerTextureSize - 1);
int texPixelZ = Mathf.Clamp(Mathf.RoundToInt(texCoordZ), 0, LayerTextureSize - 1);

Key Notes to Avoid Issues #

• Axis Alignment: Double-check that your texture's axis direction matches your terrain's. For example, if your texture's Y-axis starts at the top but your terrain's Z-axis starts at the bottom, you may need to flip the texture coordinate like texPixelY = LayerTextureSize - 1 - texPixelZ.
• Boundary Handling: The Clamp function ensures you don't access pixels outside the texture's bounds (e.g., when the hit point is exactly on the chunk edge, which would otherwise give 128—an invalid index for a 128x128 texture).
• UV Coordinate Alternative: If you're using texture UVs (0 to 1 range) instead of pixel indices, skip the scale factor and just divide the local coordinates by ChunkSize: float uvX = localX / ChunkSize;—this works because the GPU will automatically map the 0-1 UV range to the 128x128 texture's pixels.

This logic extends to any chunk/texture size ratio—you just adjust the scaleFactor accordingly. The same core idea worked when sizes were equal because the scale factor was 1, which simplified the math!

内容的提问来源于stack exchange，提问作者Swiftprog