Hi,

I have terrain code with fancy stuff done but everything is read from files (heightmaps, blendmaps etc.). I would like to make editing possible on runtime, like pushing the heightmap or painting with textures. My problem is I don't know how to get texture coordinates of place on map I picked with cursor. For example to paint a road on terrain with sand texture.

Also I am using tessellation + displacement mapping, so my vertex buffer cotains simple quad, which makes host side closest ray-triangle itersection test rather useless. Another thing is that I can use compute shader (I got access to dx11 features in my XNA project), so I have possibility to speed things up I am also using deffered shading so I got depth buffer stored in render target texture (maybe I can use that somehow?).

Any ideas how I can achieve what I want to do?

Other option would be to just pre-tesselate the mesh and use that for picking and rendering.

That's good idea, thanks:) I also have been thinking about editing textures directly with model preview. I will try both options and see which is more convenient :)

If someone got other ideas and tips for terrain editors I will be thankful for sharing :)

I did with very simple method. I sent to shader my cursor position in screen space. I read depth in that position from my depth buffer, then I did depth to world position transformation, that way I get the point my cursor is picking. Since I know my terrain position and dimmensions, I simply do (pickedPoint.xz-TerrainMinValue)/TerrainMaxValue - this way I get picked texture coordinate on my terrain displacement map. It works fine :)