Discard a geometry inside 4 points

[Daoudou]

Hello everyone

I would need help.

I have a surface created with geometry and I would like to cut out part of the surface to place an object on it without the surface being inside the object (I have an open boat and the blue surface crosses the boat and is therefore visible inside). (see picture)

For this I have 4 corner points and I would like to delete the geometry and primitives located inside these 4 corners. (the white square on the image)

For this how could I proceed?

A solution would be to obtain the position of these 4 points in a shader and to delete the fragments inside with the "discrad" method in glsl if I'm not mistaken? (However I don't have enough knowledge with shaders ^^')

Or do you have any other suggestions?

i found this source :

[osg-users] [osgOcean] Culling and intersects with ocean and model...

Thanks in advance
Cordially

[robertosfield]

I can't figure out specifically what you need from your description so it's not possible to give specific advice.

Is it just rendering that you need to alter, or do you need to modify the mesh and vertex data or geometry?

How is the original geometry created? How is the hole controlled?

[Daoudou]

hello

I need to modify only the rendering, for the original geometry I only have a cube and for the hole I pass specific coordinates manually for the 4 points.

[robertosfield]

Stencil buffer might be useful for doing cutouts. You'd render the cutout geometry to the stencil buffer then in main pass check the stencil buffer to decide which fragments to render or not. You can do something similar with use render to texture.

[Daoudou]

Okay and if i want to do it with only to modify the mesh and vertex data ? It will work the same way ? With Stencil buffer ?

[LaurensVoerman]

You might be able to render the water surface first, and not write into the depth buffer, so anything rendered later will overwrite the pixels. Here is an example in that vein: (it does write the depth buffer , but always "1" (far clip plane) Regards, Laurens. StateSet { DataVariance STATIC rendering_hint DEFAULT_BIN renderBinMode USE binNumber -1 binName RenderBin GL_CULL_FACE OVERRIDE|OFF GL_LIGHTING OVERRIDE|OFF GL_DEPTH_TEST ON Depth { function ALWAYS writeMask TRUE range 1 1 } }

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