Added heightmap example (#206)

* added heightmap example

* better formatting

build.zig

@@ -373,11 +373,11 @@ pub fn build(b: *std.Build) !void {
             .desc = "Image loading and texture creation",
         },
 
-        // .{
+        .{
-        //     .name = "models_loading",
+            .name = "models_heightmap",
-        //     .path = "examples/models/models_loading.zig",
+            .path = "examples/models/models_heightmap.zig",
-        //     .desc = "Loads a model and renders it",
+            .desc = "Heightmap loading and drawing",
-        // },
+        },
         // .{
         //     .name = "shaders_basic_lighting",
         //     .path = "examples/shaders/shaders_basic_lighting.zig",

examples/models/models_heightmap.zig

@@ -0,0 +1,49 @@
+const rl = @import("raylib");
+
+pub fn main() anyerror!void {
+    const screenWidth: i32 = 800;
+    const screenHeight: i32 = 450;
+
+    rl.initWindow(screenWidth, screenHeight, "raylib [models] example - heightmap loading and drawing");
+    const cameraPosition: rl.Vector3 = .{ .x = 18, .y = 21, .z = 18 };
+    const cameraTarget: rl.Vector3 = .{ .x = 0, .y = 0, .z = 0 };
+    const cameraUp: rl.Vector3 = .{ .x = 0, .y = 1, .z = 0 };
+    const cameraProjection = rl.CameraProjection.perspective;
+    var camera = rl.Camera{ .fovy = 45.0, .position = cameraPosition, .up = cameraUp, .projection = cameraProjection, .target = cameraTarget };
+
+    const image: rl.Image = try rl.loadImage("examples/models/resources/heightmap.png");
+
+    const texture: rl.Texture2D = try rl.loadTextureFromImage(image);
+
+    const meshSize = rl.Vector3{ .x = 16, .y = 8, .z = 16 };
+    const mesh = rl.genMeshHeightmap(image, meshSize);
+
+    var model = try rl.loadModelFromMesh(mesh);
+    model.materials[0].maps[@intFromEnum(rl.MATERIAL_MAP_DIFFUSE)].texture = texture;
+
+    const mapPosition = rl.Vector3{ .x = -8.0, .y = 0.0, .z = -8.0 };
+
+    rl.unloadImage(image);
+
+    rl.setTargetFPS(60);
+
+    while (!rl.windowShouldClose()) {
+        rl.updateCamera(&camera, rl.CameraMode.orbital);
+        rl.beginDrawing();
+
+        rl.clearBackground(rl.Color.ray_white);
+        rl.beginMode3D(camera);
+        rl.drawModel(model, mapPosition, 1, rl.Color.red);
+        rl.drawGrid(20, 1.0);
+        rl.endMode3D();
+        rl.drawTexture(texture, screenWidth - texture.width - 20, 20, rl.Color.white);
+        rl.drawRectangleLines(screenWidth - texture.width - 20, 20, texture.width, texture.height, rl.Color.green);
+        rl.drawFPS(10, 10);
+
+        rl.endDrawing();
+    }
+    rl.unloadTexture(texture);
+    rl.unloadModel(model);
+
+    rl.closeWindow();
+}