rlgl Vertex level operations and Draw Textured Polygon Example.

examples/draw_textured_polygon/main.lua

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+-- Based on raylib example - Draw Textured Polygon by Chris Camacho (@codifies)
+
+package.path = package.path..";"..RL.GetBasePath().."../resources/lib/?.lua"
+
+Vec2 = require( "vector2" )
+
+local monitor = 0
+local mPos = Vec2:new( RL.GetMonitorPosition( monitor ) )
+local mSize = Vec2:new( RL.GetMonitorSize( monitor ) )
+local winSize = Vec2:new( RL.GetScreenSize() )
+
+local polygon = {
+	texture = -1,
+	texcoords = {
+		Vec2:new( 0.75, 0.0 ),
+		Vec2:new( 0.25, 0.0 ),
+		Vec2:new( 0.0, 0.5 ),
+		Vec2:new( 0.0, 0.75 ),
+		Vec2:new( 0.25, 1.0 ),
+		Vec2:new( 0.375, 0.875 ),
+		Vec2:new( 0.625, 0.875 ),
+		Vec2:new( 0.75, 1.0 ),
+		Vec2:new( 1.0, 0.75 ),
+		Vec2:new( 1.0, 0.5 ),
+		Vec2:new( 0.75, 0.0 ),
+    },
+	points = {},
+	positions = {},
+	angle = 0.0,
+}
+
+function RL.init()
+	RL.SetWindowState( RL.FLAG_WINDOW_RESIZABLE )
+	RL.SetWindowState( RL.FLAG_VSYNC_HINT )
+	RL.SetWindowPosition( { mPos.x + mSize.x / 2 - winSize.x / 2, mPos.y + mSize.y / 2 - winSize.y / 2 } )
+	RL.SetWindowTitle( "Textured Polygon" )
+
+	polygon.texture = RL.LoadTexture( RL.GetBasePath().."../resources/images/cat.png" )
+
+	-- Define the base poly vertices from the UV's
+    -- NOTE: They can be specified in any other way
+	for _, texcoord in ipairs( polygon.texcoords ) do
+		table.insert( polygon.points, Vec2:new( ( texcoord.x - 0.5 ) * 256, ( texcoord.y - 0.5 ) * 256 ) )
+	end
+
+    -- Define the vertices drawing position
+    -- NOTE: Initially same as points but updated every frame
+	for _, point in ipairs( polygon.points ) do
+		table.insert( polygon.positions, point:clone() )
+	end
+end
+
+function RL.process( delta )
+	polygon.angle = polygon.angle + delta
+
+	-- Update points rotation with an angle transform
+	-- NOTE: Base points position are not modified
+	for i = 1, #polygon.points do
+		polygon.positions[i] = Vec2:new( RL.Vector2Rotate( polygon.points[i], polygon.angle ) )
+	end
+end
+
+-- Draw textured polygon, defined by vertex and texture coordinates
+-- NOTE: Polygon center must have straight line path to all points
+-- without crossing perimeter, points must be in anticlockwise order
+local function drawTexturePoly( texture, center, points, texcoords, tint )
+	RL.rlSetTexture( RL.GetTextureId( texture ) )
+
+	-- Texturing is only supported on RL_QUADS
+	RL.rlBegin( RL.RL_QUADS )
+		RL.rlColor4ub( tint )
+
+		for i = 1, #points - 1 do
+			RL.rlTexCoord2f( { 0.5, 0.5 } )
+			RL.rlVertex2f( center )
+
+			RL.rlTexCoord2f( texcoords[i] )
+			RL.rlVertex2f( center + points[i] )
+
+			RL.rlTexCoord2f( texcoords[i + 1] )
+			RL.rlVertex2f( center + points[i + 1] )
+			-- Dublicate of last vertex to complete quad.
+			RL.rlTexCoord2f( texcoords[i + 1] )
+			RL.rlVertex2f( center + points[i + 1] )
+		end
+	RL.rlEnd()
+end
+
+function RL.draw()
+	RL.ClearBackground( RL.RAYWHITE )
+
+	drawTexturePoly( polygon.texture, winSize:scale( 0.5 ), polygon.positions, polygon.texcoords, RL.WHITE )
+end