add custom-models in hand support

src/graphics/render/MainBatch.cpp

@@ -80,3 +80,56 @@ glm::vec4 MainBatch::sampleLight(
         glm::max(Lightmap::extract(light, 3), minIntensity) / 15.0f
     );
 }
+
+inline glm::vec4 do_tint(float value) {
+    return glm::vec4(value, value, value, 1.0f);
+}
+
+void MainBatch::cube(
+    const glm::vec3& coord,
+    const glm::vec3& size,
+    const UVRegion(&texfaces)[6],
+    const glm::vec4& tint,
+    bool shading
+) {
+    const glm::vec3 X(1.0f, 0.0f, 0.0f);
+    const glm::vec3 Y(0.0f, 1.0f, 0.0f);
+    const glm::vec3 Z(0.0f, 0.0f, 1.0f);
+
+    quad(
+        coord + glm::vec3(0.0f, 0.0f, 0.0f),
+        X, Y, glm::vec2(size.x, size.y),
+        (shading ? do_tint(0.8) * tint : tint),
+        glm::vec3(1.0f), texfaces[5]
+    );
+    quad(
+        coord + glm::vec3(size.x, 0.0f, -size.z),
+        -X, Y, glm::vec2(size.x, size.y),
+        (shading ? do_tint(0.8) * tint : tint),
+        glm::vec3(1.0f), texfaces[4]
+    );
+    quad(
+        coord + glm::vec3(0.0f, size.y, 0.0f),
+        X, -Z, glm::vec2(size.x, size.z),
+        (shading ? do_tint(1.0f) * tint : tint),
+        glm::vec3(1.0f), texfaces[3]
+    );
+    quad(
+        coord + glm::vec3(0.0f, 0.0f, -size.z),
+        X, Z, glm::vec2(size.x, size.z),
+        (shading ? do_tint(0.7f) * tint : tint),
+        glm::vec3(1.0f), texfaces[2]
+    );
+    quad(
+        coord + glm::vec3(0.0f, 0.0f, -size.z),
+        Z, Y, glm::vec2(size.z, size.y),
+        (shading ? do_tint(0.9f) * tint : tint),
+        glm::vec3(1.0f), texfaces[0]
+    );
+    quad(
+        coord + glm::vec3(size.x, 0.0f, 0.0f),
+        -Z, Y, glm::vec2(size.z, size.y),
+        (shading ? do_tint(0.9f) * tint : tint),
+        glm::vec3(1.0f), texfaces[1]
+    );
+}