raylib-cs/Examples/Textures/Polygon.cs

/*******************************************************************************************
*
*   raylib [shapes] example - Draw Textured Polygon
*
*   This example has been created using raylib 99.98 (www.raylib.com)
*   raylib is licensed under an unmodified zlib/libpng license (View raylib.h for details)
*
*   Copyright (c) 2014 Ramon Santamaria (@raysan5)
*   Copyright (c) 2021 Chris Camacho (codifies - bedroomcoders.co.uk)
*
********************************************************************************************/

using System.Numerics;
using static Raylib_cs.Raylib;

namespace Examples.Textures;

public class Polygon
{
    public static int Main()
    {
        // Initialization
        //--------------------------------------------------------------------------------------
        const int screenWidth = 800;
        const int screenHeight = 450;

        InitWindow(screenWidth, screenHeight, "raylib [textures] example - Textured Polygon");

        Vector2[] texcoords = new[] {
                new Vector2(0.75f, 0),
                new Vector2(0.25f, 0),
                new Vector2(0, 0.5f),
                new Vector2(0, 0.75f),
                new Vector2(0.25f, 1),
                new Vector2(0.375f, 0.875f),
                new Vector2(0.625f, 0.875f),
                new Vector2(0.75f, 1),
                new Vector2(1, 0.75f),
                new Vector2(1, 0.5f),
                // Close the poly
                new Vector2(0.75f, 0)
            };

        Vector2[] points = new Vector2[11];

        // Define the base poly vertices from the UV's
        // NOTE: They can be specified in any other way
        for (int i = 0; i < points.Length; i++)
        {
            points[i].X = (texcoords[i].X - 0.5f) * 256.0f;
            points[i].Y = (texcoords[i].Y - 0.5f) * 256.0f;
        }

        // Define the vertices drawing position
        // NOTE: Initially same as points but updated every frame
        Vector2[] positions = new Vector2[points.Length];
        for (int i = 0; i < positions.Length; i++)
        {
            positions[i] = points[i];
        }

        Texture2D texture = LoadTexture("resources/cat.png");
        float angle = 0;

        SetTargetFPS(60);
        //--------------------------------------------------------------------------------------

        // Main game loop
        while (!WindowShouldClose())
        {
            // Update
            //----------------------------------------------------------------------------------
            // Update your variables here
            //----------------------------------------------------------------------------------
            angle += 1;
            for (int i = 0; i < positions.Length; i++)
            {
                positions[i] = Raymath.Vector2Rotate(points[i], angle * Raylib.DEG2RAD);
            }

            // Draw
            //----------------------------------------------------------------------------------
            BeginDrawing();
            ClearBackground(Color.RAYWHITE);

            DrawText("Textured Polygon", 20, 20, 20, Color.DARKGRAY);
            Vector2 center = new(screenWidth / 2, screenHeight / 2);
            DrawTexturePoly(texture, center, positions, texcoords, positions.Length, Color.WHITE);

            EndDrawing();
            //----------------------------------------------------------------------------------
        }

        UnloadTexture(texture);

        // De-Initialization
        //--------------------------------------------------------------------------------------
        CloseWindow();
        //--------------------------------------------------------------------------------------

        return 0;
    }

    // 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
    static void DrawTexturePoly(
        Texture2D texture,
        Vector2 center,
        Vector2[] points,
        Vector2[] texcoords,
        int pointCount,
        Color tint
    )
    {
        Rlgl.SetTexture(texture.Id);

        // Texturing is only supported on RL_QUADS
        Rlgl.Begin(DrawMode.QUADS);

        Rlgl.Color4ub(tint.R, tint.G, tint.B, tint.A);

        for (int i = 0; i < pointCount - 1; i++)
        {
            Rlgl.TexCoord2f(0.5f, 0.5f);
            Rlgl.Vertex2f(center.X, center.Y);

            Rlgl.TexCoord2f(texcoords[i].X, texcoords[i].Y);
            Rlgl.Vertex2f(points[i].X + center.X, points[i].Y + center.Y);

            Rlgl.TexCoord2f(texcoords[i + 1].X, texcoords[i + 1].Y);
            Rlgl.Vertex2f(points[i + 1].X + center.X, points[i + 1].Y + center.Y);

            Rlgl.TexCoord2f(texcoords[i + 1].X, texcoords[i + 1].Y);
            Rlgl.Vertex2f(points[i + 1].X + center.X, points[i + 1].Y + center.Y);
        }
        Rlgl.End();

        Rlgl.SetTexture(0);
    }
}