63 lines
1.4 KiB
Lua
63 lines
1.4 KiB
Lua
--- Mesh utilities
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-- @module mesh
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local modules = (...):gsub('%.[^%.]+$', '') .. "."
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local vec3 = require(modules .. "vec3")
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local mesh = {}
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-- vertices is an arbitrary list of vec3s
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function mesh.average(vertices)
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local out = vec3()
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for _, v in ipairs(vertices) do
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out:add(out, v)
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end
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return out:div(out, #vertices)
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end
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-- triangle[1] is a vec3
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-- triangle[2] is a vec3
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-- triangle[3] is a vec3
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function mesh.normal(triangle)
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local ca = vec3():sub(triangle[3], triangle[1])
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local ba = vec3():sub(triangle[2], triangle[1])
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local out = vec3()
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return out
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:cross(ca, ba)
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:normalize(out)
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end
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-- triangle[1] is a vec3
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-- triangle[2] is a vec3
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-- triangle[3] is a vec3
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function mesh.plane_from_triangle(triangle)
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local out = {}
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local ca = vec3():sub(triangle[3], triangle[1])
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local ba = vec3():sub(triangle[2], triangle[1])
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out.origin = triangle[1]
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out.normal = vec3()
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:cross(ba, ca)
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:normalize(out)
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out.dot = -out.normal:dot(out.origin)
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return out
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end
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-- plane.origin is a vec3
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-- plane.normal is a vec3
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-- direction is a vec3
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function mesh.is_front_facing(plane, direction)
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return plane.normal:dot(direction) <= 0
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end
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-- point is a vec3
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-- plane.origin is a vec3
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-- plane.normal is a vec3
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-- plane.dot is a number
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function mesh.signed_distance(point, plane)
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dot = plane.dot or -plane.normal:dot(plane.origin)
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return point:dot(plane.normal) + dot
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end
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return mesh
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