Update/merge examples back into main repo (#192)

Examples/Shaders/Eratosthenes.cs

@@ -0,0 +1,103 @@
+/*******************************************************************************************
+*
+*   raylib [shaders] example - Sieve of Eratosthenes
+*
+*   Sieve of Eratosthenes, the earliest known (ancient Greek) prime number sieve.
+*
+*   "Sift the twos and sift the threes,
+*    The Sieve of Eratosthenes.
+*    When the multiples sublime,
+*    the numbers that are left are prime."
+*
+*   NOTE: This example requires raylib OpenGL 3.3 or ES2 versions for shaders support,
+*         OpenGL 1.1 does not support shaders, recompile raylib to OpenGL 3.3 version.
+*
+*   NOTE: Shaders used in this example are #version 330 (OpenGL 3.3).
+*
+*   This example has been created using raylib 2.5 (www.raylib.com)
+*   raylib is licensed under an unmodified zlib/libpng license (View raylib.h for details)
+*
+*   Example contributed by ProfJski and reviewed by Ramon Santamaria (@raysan5)
+*
+*   Copyright (c) 2019 ProfJski and Ramon Santamaria (@raysan5)
+*
+********************************************************************************************/
+
+using System.Numerics;
+using static Raylib_cs.Raylib;
+
+namespace Examples.Shaders;
+
+public class Eratosthenes
+{
+    const int GlslVersion = 330;
+
+    public static int Main()
+    {
+        // Initialization
+        //--------------------------------------------------------------------------------------
+        const int screenWidth = 800;
+        const int screenHeight = 450;
+
+        InitWindow(screenWidth, screenHeight, "raylib [shaders] example - Sieve of Eratosthenes");
+
+        RenderTexture2D target = LoadRenderTexture(screenWidth, screenHeight);
+
+        // Load Eratosthenes shader
+        // NOTE: Defining 0 (NULL) for vertex shader forces usage of internal default vertex shader
+        Shader shader = LoadShader(null, $"resources/shaders/glsl{GlslVersion}/eratosthenes.fs");
+
+        SetTargetFPS(60);
+        //--------------------------------------------------------------------------------------
+
+        // Main game loop
+        while (!WindowShouldClose())
+        {
+            // Update
+            //----------------------------------------------------------------------------------
+            // Nothing to do here, everything is happening in the shader
+            //----------------------------------------------------------------------------------
+
+            // Draw
+            //----------------------------------------------------------------------------------
+            BeginDrawing();
+            ClearBackground(Color.RAYWHITE);
+
+            // Enable drawing to texture
+            BeginTextureMode(target);
+            ClearBackground(Color.BLACK);
+
+            // Draw a rectangle in shader mode to be used as shader canvas
+            // NOTE: Rectangle uses font white character texture coordinates,
+            // so shader can not be applied here directly because input vertexTexCoord
+            // do not represent full screen coordinates (space where want to apply shader)
+            DrawRectangle(0, 0, GetScreenWidth(), GetScreenHeight(), Color.BLACK);
+
+            // End drawing to texture (now we have a blank texture available for the shader)
+            EndTextureMode();
+
+            BeginShaderMode(shader);
+            // NOTE: Render texture must be y-flipped due to default OpenGL coordinates (left-bottom)
+            DrawTextureRec(
+                target.Texture,
+                new Rectangle(0, 0, target.Texture.Width, -target.Texture.Height),
+                new Vector2(0.0f, 0.0f),
+                Color.WHITE
+            );
+            EndShaderMode();
+
+            EndDrawing();
+            //----------------------------------------------------------------------------------
+        }
+
+        // De-Initialization
+        //--------------------------------------------------------------------------------------
+        UnloadShader(shader);
+        UnloadRenderTexture(target);
+
+        CloseWindow();
+        //--------------------------------------------------------------------------------------
+
+        return 0;
+    }
+}