From 3275ae4948fd2c1bb8da780214cbb741dc3178be Mon Sep 17 00:00:00 2001
From: sanine <sanine.not@pm.me>
Date: Fri, 12 May 2023 01:16:46 -0500
Subject: begin refactor

---
 honey/asset/mesh.lua | 150 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 150 insertions(+)
 create mode 100644 honey/asset/mesh.lua

(limited to 'honey/asset/mesh.lua')

diff --git a/honey/asset/mesh.lua b/honey/asset/mesh.lua
new file mode 100644
index 0000000..876c5e4
--- /dev/null
+++ b/honey/asset/mesh.lua
@@ -0,0 +1,150 @@
+local gl = honey.gl
+
+local module = {}
+setmetatable(module, {__index=_G})
+setfenv(1, module)
+
+
+-- append the 8 floats per vertex to the vertices table
+local function insertVertex(vertices, attrib, vertex)
+	local pos = 3*vertex.v_idx
+	for i=1,3 do
+		table.insert(vertices, attrib.vertices[pos+i])
+	end
+
+	local normal = 3*vertex.vn_idx
+	for i=1,3 do
+		table.insert(vertices, attrib.normals[normal+i])
+	end
+
+	local tex = 2*vertex.vt_idx
+	for i=1,2 do
+		table.insert(vertices, attrib.texcoords[tex+i])
+	end
+end
+
+
+-- creates a table of floats representing vertex data
+-- and a table of ints representing face indices within the vertices
+local function loadShape(shape, attrib, debug)
+	local vertices = {}
+	local indices = {}
+
+	local start = shape.face_offset
+	local finish = start + shape.length
+	for i=start,finish-1 do
+		assert(attrib.face_num_verts[i+1] == 3, "non-triangular face!")
+		for j=0,2 do
+			local vertex = attrib.faces[(3*i) + j + 1]
+			insertVertex(vertices, attrib, vertex, debug)
+			table.insert(indices, #indices)
+		end
+	end
+
+	return vertices, indices
+end
+
+
+-- public helper function (used in some other places, like trimesh construction)
+-- packages the vertices & indices tables from loadShape into a single array
+loadFile = function(filename)
+	local flags = honey.tinyobj.FLAG_TRIANGULATE
+	local attrib, shapes, materials = honey.tinyobj.parse_obj(filename, flags)
+	
+	local meshes = {}
+	for _, shape in ipairs(shapes) do
+		local vertices, indices = loadShape(shape, attrib, debug)
+		table.insert(meshes, {vertices=vertices, indices=indices})
+	end
+	return meshes
+end
+
+
+-- helper function to create a gl vertex array object from (vertices, indices) pair
+local function createMesh(vertices, indices)
+	vao = gl.GenVertexArrays()
+	vbo = gl.GenBuffers()
+	ebo = gl.GenBuffers()
+
+	gl.BindVertexArray(vao)
+	gl.BindBuffer(gl.ARRAY_BUFFER, vbo)
+	gl.BufferData(gl.ARRAY_BUFFER, gl.FLOAT, vertices, gl.STATIC_DRAW)
+
+	gl.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, ebo)
+	gl.BufferData(gl.ELEMENT_ARRAY_BUFFER, gl.UNSIGNED_INT, indices, gl.STATIC_DRAW)
+
+	local stride = 8
+	local offset = 0
+	
+	-- position
+	gl.VertexAttribPointer(0, 3, false, stride, offset)
+	gl.EnableVertexAttribArray(0)
+	offset = offset+3
+
+	-- normal
+	gl.VertexAttribPointer(1, 3, false, stride, offset)
+	gl.EnableVertexAttribArray(1)
+	offset = offset+3
+
+	-- texture
+	gl.VertexAttribPointer(2, 2, false, stride, offset)
+	gl.EnableVertexAttribArray(2)
+	offset = offset+2
+
+	return vao, vbo, ebo, #vertices
+end
+
+
+local cache = {}
+
+
+-- get a gl vertex array object + vertex count
+get = function(filename, index)
+	if not cache[filename] then
+		local c = {}
+		local meshes = loadFile(filename)
+		for _, m in ipairs(meshes) do
+			local vao, vbo, ebo, count = createMesh(m.vertices, m.indices)
+			table.insert(c, { vao=vao, vbo=vbo, ebo=ebo, count=count })
+		end
+		cache[filename] = c
+	end
+	local m = cache[filename][index]
+	return m.vao, m.count
+end
+
+
+-- forget a mesh
+forget = function(filename)
+	if not cache[filename] then return end
+	for _, m in ipairs(cache[filename]) do
+		gl.DeleteBuffers(m.vbo)
+		gl.DeleteBuffers(m.ebo)
+		gl.DeleteVertexArrays(m.vao)
+	end
+	cache[filename] = nil
+end
+
+
+-- clear the cache
+clearCache = function()
+	for key in pairs(cache) do
+		forget(key)
+	end
+end
+
+
+--===== builtin meshes =====--
+
+function createBuiltins()
+	cache["builtin.quad"] = {Mesh(
+		{ 0, 0, 0,   0, 1, 0,   0, 0,
+		  1, 0, 0,   0, 1, 0,   1, 0,
+		  0, 1, 0,   0, 1, 0,   0, 1,
+		  1, 1, 0,   0, 1, 0,   1, 1 },
+		{ 0, 1, 3, 0, 3, 2 }
+	)}
+end
+
+
+return module 
-- 
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