Demos (master): torus.c: Lighting effect is distorted when object is scaled up/down

[Brian Paul]

Module: Demos
Branch: master
Commit: a56afc865e95bfc5e9748d015f344ad58aafdc22
URL:    http://cgit.freedesktop.org/mesa/demos/commit/?id=a56afc865e95bfc5e9748d015f344ad58aafdc22

Author: Dongwon Kim <dongwon.kim at intel.com>
Date:   Tue Feb  3 15:48:00 2015 -0700

torus.c: Lighting effect is distorted when object is scaled up/down

When torus object is scaled up/down via glScalef call the lighting
effect is incorrectly expressed on render target because normals'
length is also changed when vertices are scaled up/down.

This patch enables "automatic normalization" of normals, which
is one of well-known ways to avoid this kind of distortion.

Reference:
www.opengl.org/sdk/docs/man2/xhtml/glScale.xml

Notes

 If scale factors other than 1 are applied to the modelview matrix
 and lighting is enabled, lighting often appears wrong.
 In that case, enable automatic normalization of normals by
 calling glEnable with the argument GL_NORMALIZE.

Signed-off-by: Dongwon Kim <dongwon.kim at intel.com>
Reviewed-by: Brian Paul <brianp at vmware.com>

---

 src/egl/opengles1/torus.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/egl/opengles1/torus.c b/src/egl/opengles1/torus.c
index 8f262b5..ccf53d1 100644
--- a/src/egl/opengles1/torus.c
+++ b/src/egl/opengles1/torus.c
@@ -358,6 +358,11 @@ init(void)
 
    make_texture();
    glEnable(GL_TEXTURE_2D);
+
+   /* Enable automatic normalizing to get proper lighting when torus is
+    * scaled down via glScalef
+    */
+   glEnable(GL_NORMALIZE);
 }