cambridge/tetris/components/draw_block.lua

local mat4 = cpml.mat4
local vec3 = cpml.vec3

local cube = {
	front = {},
	top = {},
	bottom = {},
	left = {},
	right = {}
}
for scale = 1,2 do
	cube.front[scale] = love.graphics.newMesh(
		{
			{ "VertexPosition", "float", 3 },
			{ "VertexTexCoord", "float", 2 },
			{ "VertexColor", "byte", 4}
		},
		{
			{
				0, 0, 0,
				0, 0,
				1, 1, 1
			},

			{
				16*scale, 0, 0,
				1, 0,
				1, 1, 1,
			},

			{
				0, 16*scale, 0,
				0, 1,
				1, 1, 1,
			},

			{
				16*scale, 16*scale, 0,
				1, 1,
				1, 1, 1,
			},
		},
		"strip",
		"static"
	)
	cube.top[scale] = love.graphics.newMesh(
		{
			{ "VertexPosition", "float", 3 },
			{ "VertexTexCoord", "float", 2 },
			{ "VertexColor", "byte", 4}
		},
		{
			{
				0, 0, 0,
				0, 0,
				1, 1, 1
			},

			{
				16*scale, 0, 0,
				1, 0,
				1, 1, 1,
			},

			{
				0, 0, 16*scale,
				0, 1,
				1, 1, 1,
			},

			{
				16*scale, 0, 16*scale,
				1, 1,
				1, 1, 1,
			},
		},
		"strip",
		"static"
	)
	cube.bottom[scale] = love.graphics.newMesh(
		{
			{ "VertexPosition", "float", 3 },
			{ "VertexTexCoord", "float", 2 },
			{ "VertexColor", "byte", 4}
		},
		{
			{
				0, 16*scale, 16*scale,
				0, 0,
				1, 1, 1
			},

			{
				16*scale, 16*scale, 16*scale,
				1, 0,
				1, 1, 1,
			},

			{
				0, 16*scale, 0,
				0, 1,
				1, 1, 1,
			},

			{
				16*scale, 16*scale, 0,
				1, 1,
				1, 1, 1,
			},
		},
		"strip",
		"static"
	)
	cube.left[scale] = love.graphics.newMesh(
		{
			{ "VertexPosition", "float", 3 },
			{ "VertexTexCoord", "float", 2 },
			{ "VertexColor", "byte", 4}
		},
		{
			{
				0, 0, 0,
				0, 0,
				1, 1, 1
			},

			{
				0, 16*scale, 0,
				1, 0,
				1, 1, 1,
			},

			{
				0, 0, 16*scale,
				0, 1,
				1, 1, 1,
			},

			{
				0, 16*scale, 16*scale,
				1, 1,
				1, 1, 1,
			},
		},
		"strip",
		"static"
	)
	cube.right[scale] = love.graphics.newMesh(
		{
			{ "VertexPosition", "float", 3 },
			{ "VertexTexCoord", "float", 2 },
			{ "VertexColor", "byte", 4}
		},
		{
			{
				16*scale, 16*scale, 16*scale,
				0, 0,
				1, 1, 1
			},

			{
				16*scale, 0, 16*scale,
				1, 0,
				1, 1, 1,
			},

			{
				16*scale, 16*scale, 0,
				0, 1,
				1, 1, 1,
			},

			{
				16*scale, 0, 0,
				1, 1,
				1, 1, 1,
			},
		},
		"strip",
		"static"
	)
end

local shader_no_discard = {
	shader = love.graphics.newShader(
		[[
		vec4 effect(vec4 color, Image tex, vec2 texture_coords, vec2 screen_coords) {
			vec4 texcolor = Texel(tex, texture_coords);
			return texcolor * color;
		}
		]],
		[[
		uniform mat4 transform;
		vec4 position(mat4 transform_projection, vec4 vertex_position) {
			return transform * TransformMatrix * (vertex_position - vec4(vec2(640.0, 480.0) / 2.0, 0.0, 0.0));
		}
		]]
	),
	width = -1,
	height = -1,
	depth_3d = -1
}
local shader_discard = {
	shader = love.graphics.newShader(
		[[
		uniform vec4 rect;
		vec4 effect(vec4 color, Image tex, vec2 texture_coords, vec2 screen_coords) {
			if (screen_coords.x < rect.x || screen_coords.x > rect.y || screen_coords.y < rect.z || screen_coords.y > rect.w) discard;
			vec4 texcolor = Texel(tex, texture_coords);
			return texcolor * color;
		}
		]],
		[[
		uniform mat4 transform;
		vec4 position(mat4 transform_projection, vec4 vertex_position) {
			return transform * TransformMatrix * (vertex_position - vec4(vec2(640.0, 480.0) / 2.0, 0.0, 0.0));
		}
		]]
	),
	width = -1,
	height = -1,
	depth_3d = -1
}

local function set_shader_transform(shader, width, height)
	local depth = (480 / 2) / math.tan(math.rad(config.depth_3d) / 2)
	local look_at = mat4():look_at(vec3(0, 0, depth), vec3(0, 0, 0), vec3(0, 1, 0))
	local perspective = mat4.from_perspective(config.depth_3d, width / height, -0.5, 0.5)
	local tall = height / 480 > width / 640
	if tall then
		local scale_factor = (480 * width) / (640 * height)
		shader:send("transform", mat4.scale(mat4.new(), perspective * look_at, vec3(scale_factor)))
	else
		shader:send("transform", perspective * look_at)
	end
end

return function(R, G, B, A, image, x, y, left, right, top, bottom, big)
	local scale = big and 2 or 1
	if config.depth_3d > 0 then
		love.graphics.setCanvas{GLOBAL_CANVAS, depth = true}
		love.graphics.push()
		love.graphics.origin()
		love.graphics.setDepthMode("lequal", true)
		local shader
		local current_width = love.graphics.getWidth()
		local current_height = love.graphics.getHeight()
		if left and right and top and bottom then
			love.graphics.setShader(shader_discard.shader)
			local scale_factor = math.min(current_width / 640, current_height / 480)
			local rect_left = (current_width - scale_factor * 640) / 2 + left * scale_factor
			local rect_right = (current_width - scale_factor * 640) / 2 + right * scale_factor
			local rect_top = (current_height - scale_factor * 480) / 2 + top * scale_factor
			local rect_bottom = (current_height - scale_factor * 480) / 2 + bottom * scale_factor
			shader_discard.shader:send("rect", {rect_left, rect_right, rect_top, rect_bottom})
			shader = shader_discard
		else
			love.graphics.setShader(shader_no_discard.shader)
			shader = shader_no_discard
		end
		if current_width ~= shader.width or current_height ~= shader.height or config.depth_3d ~= shader.depth_3d then
			set_shader_transform(shader.shader, current_width, current_height)
			shader.width = current_width
			shader.height = current_height
			shader.depth_3d = config.depth_3d
		end

		if A ~= 1 or y > 480 / 2 then
			love.graphics.setColor(R, G, B, A)
			cube.top[scale]:setTexture(image)
			love.graphics.draw(cube.top[scale], x, y)
		end

		love.graphics.setColor(R / 2, G / 2, B / 2, A)
		if A ~= 1 or y < 480 / 2 then
			cube.bottom[scale]:setTexture(image)
			love.graphics.draw(cube.bottom[scale], x, y)
		end
		if A ~= 1 or x > 640 / 2 then
			cube.left[scale]:setTexture(image)
			love.graphics.draw(cube.left[scale], x, y)
		end
		if A ~= 1 or x < 640 / 2 then
			cube.right[scale]:setTexture(image)
			love.graphics.draw(cube.right[scale], x, y)
		end

		love.graphics.setColor(R, G, B, A)
		cube.front[scale]:setTexture(image)
		love.graphics.draw(cube.front[scale], x, y)

		love.graphics.setShader()
		love.graphics.setDepthMode()
		love.graphics.pop()
		love.graphics.setCanvas(GLOBAL_CANVAS)
	else
		love.graphics.setColor(R, G, B, A)
		love.graphics.draw(image, x, y, 0, scale, scale)
	end
end