[rmodels] More performant point cloud rendering with DrawModelPoints() (#4203)

* Added the ability to draw a model as a point cloud

* Added example to demonstrate drawing a model as a point cloud

* polished the demo a bit

* picture for example

* adhere to conventions for example

* update png to match aspect ratio

* minor changes

* address code convention comments

* added point rendering to makefiles

* added point rendering to readme and renumbered examples

* comment formatting

---------

Co-authored-by: Reese Gallagher <re325479@ucf.edu.com>
Co-authored-by: Ray <raysan5@gmail.com>

examples/models/models_point_rendering.c

@@ -0,0 +1,171 @@
+/*******************************************************************************************
+*
+*   raylib example - point rendering
+*
+*   Example originally created with raylib 5.0, last time updated with raylib 5.0
+*
+*   Example contributed by Reese Gallagher (@satchelfrost) and reviewed by Ramon Santamaria (@raysan5)
+*
+*   Example licensed under an unmodified zlib/libpng license, which is an OSI-certified,
+*   BSD-like license that allows static linking with closed source software
+*
+*   Copyright (c) 2024 Reese Gallagher (@satchelfrost)
+*
+********************************************************************************************/
+
+#include "raylib.h"
+#include <stdlib.h>         // Required for: rand()
+#include <math.h>           // Required for: cos(), sin()
+
+#define MAX_POINTS 10000000 // 10 million
+#define MIN_POINTS 1000     // 1 thousand
+
+static float RandFloat();
+
+//------------------------------------------------------------------------------------
+// Program main entry point
+//------------------------------------------------------------------------------------
+int main()
+{
+    // Initialization
+    //--------------------------------------------------------------------------------------
+    const int screenWidth = 800;
+    const int screenHeight = 450;
+    InitWindow(screenWidth, screenHeight, "raylib [models] example - point rendering");
+    SetTargetFPS(60);
+
+    Camera camera = {
+        .position   = {3.0f, 3.0f, 3.0f},
+        .target     = {0.0f, 0.0f, 0.0f},
+        .up         = {0.0f, 1.0f, 0.0f},
+        .fovy       = 45.0f,
+        .projection = CAMERA_PERSPECTIVE,
+    };
+
+    Vector3 position = {0.0f, 0.0f, 0.0f};
+    bool useDrawModelPoints = true;
+    bool numPointsChanged = false;
+    int numPoints = 1000;
+    Mesh mesh = GenPoints(numPoints);
+    Model model = LoadModelFromMesh(mesh);
+    //--------------------------------------------------------------------------------------
+
+    // Main game loop
+    while(!WindowShouldClose())
+    {
+        // Update
+        //----------------------------------------------------------------------------------
+        UpdateCamera(&camera, CAMERA_ORBITAL);
+
+        if (IsKeyPressed(KEY_SPACE)) useDrawModelPoints = !useDrawModelPoints;
+        if (IsKeyPressed(KEY_UP))
+        {
+            numPoints = (numPoints * 10 > MAX_POINTS) ? MAX_POINTS : numPoints * 10;
+            numPointsChanged = true;
+            TraceLog(LOG_INFO, "num points %d", numPoints);
+        }
+        if (IsKeyPressed(KEY_DOWN))
+        {
+            numPoints = (numPoints / 10 < MIN_POINTS) ? MIN_POINTS : numPoints / 10;
+            numPointsChanged = true;
+            TraceLog(LOG_INFO, "num points %d", numPoints);
+        }
+
+        // upload a different point cloud size
+        if (numPointsChanged)
+        {
+            UnloadModel(model);
+            mesh = GenPoints(numPoints);
+            model = LoadModelFromMesh(mesh);
+            numPointsChanged = false;
+        }
+
+        // Draw
+        //----------------------------------------------------------------------------------
+        BeginDrawing();
+            ClearBackground(BLACK);
+            BeginMode3D(camera);
+
+                // The new method only uploads the points once to the GPU
+                if (useDrawModelPoints)
+                {
+                    DrawModelPoints(model, position, 1.0f, WHITE);
+                }
+                // The old method must continually draw the "points" (lines)
+                else
+                {
+                    for (int i = 0; i < numPoints; i++)
+                    {
+                        Vector3 pos = {
+                            .x = mesh.vertices[i * 3 + 0],
+                            .y = mesh.vertices[i * 3 + 1],
+                            .z = mesh.vertices[i * 3 + 2],
+                        };
+                        Color color = {
+                            .r = mesh.colors[i * 4 + 0],
+                            .g = mesh.colors[i * 4 + 1],
+                            .b = mesh.colors[i * 4 + 2],
+                            .a = mesh.colors[i * 4 + 3],
+                        };
+                        DrawPoint3D(pos, color);
+                    }
+                }
+
+                // Draw a unit sphere for reference
+                DrawSphereWires(position, 1.0f, 10, 10, YELLOW);
+            EndMode3D();
+
+            // Text formatting
+            Color color = WHITE;
+            int fps = GetFPS();
+            if ((fps < 30) && (fps >= 15)) color = ORANGE;
+            else if (fps < 15) color = RED;
+            DrawText(TextFormat("%2i FPS", fps), 20, 20, 40, color);
+            DrawText(TextFormat("Point Count: %d", numPoints), 20, screenHeight - 50, 40, WHITE);
+            DrawText("Up - increase points", 20, 70, 20, WHITE);
+            DrawText("Down - decrease points", 20, 100, 20, WHITE);
+            DrawText("Space - drawing function", 20, 130, 20, WHITE);
+            if (useDrawModelPoints) DrawText("DrawModelPoints()", 20, 160, 20, GREEN);
+            else DrawText("DrawPoint3D()", 20, 160, 20, RED);
+        EndDrawing();
+        //----------------------------------------------------------------------------------
+    }
+
+    // De-Initialization
+    //--------------------------------------------------------------------------------------
+    UnloadModel(model);
+    CloseWindow();
+    //--------------------------------------------------------------------------------------
+    return 0;
+}
+
+// Generate a spherical point cloud
+Mesh GenPoints(int numPoints)
+{
+    Mesh mesh = { 
+        .triangleCount = 1,
+        .vertexCount = numPoints,
+        .vertices = (float *)MemAlloc(numPoints * 3 * sizeof(float)),
+        .colors = (unsigned char*)MemAlloc(numPoints * 4 * sizeof(unsigned char)),
+    };
+
+    // https://en.wikipedia.org/wiki/Spherical_coordinate_system
+    for (int i = 0; i < numPoints; i++)
+    {
+        float theta = PI * rand() / RAND_MAX;
+        float phi   = 2.0f * PI * rand() / RAND_MAX;
+        float r     = 10.0f * rand() / RAND_MAX;
+        mesh.vertices[i * 3 + 0] = r * sin(theta) * cos(phi);
+        mesh.vertices[i * 3 + 1] = r * sin(theta) * sin(phi);
+        mesh.vertices[i * 3 + 2] = r * cos(theta);
+        Color color = ColorFromHSV(r * 360.0f, 1.0f, 1.0f);
+        mesh.colors[i * 4 + 0] = color.r;
+        mesh.colors[i * 4 + 1] = color.g;
+        mesh.colors[i * 4 + 2] = color.b;
+        mesh.colors[i * 4 + 3] = color.a;
+    }
+
+    // Upload mesh data from CPU (RAM) to GPU (VRAM) memory
+    UploadMesh(&mesh, false);
+    return mesh;
+}