Henri Verbeet : wined3d: Use dot() instead of length() in shader_glsl_nrm() .

[Alexandre Julliard]

Module: wine
Branch: master
Commit: a50546e563efad3b25222ca965a2e52a83111d95
URL:    http://source.winehq.org/git/wine.git/?a=commit;h=a50546e563efad3b25222ca965...

Author: Henri Verbeet <hverbeet(a)codeweavers.com>
Date:   Mon Jan 24 11:19:40 2011 +0100

wined3d: Use dot() instead of length() in shader_glsl_nrm().

As Eric Anholt pointed out, using length() here is suboptimal. It essentially
translates into "inversesqrt(dot(x, x));", but needs to handle the case of
zero-length vectors, much like nrm.

---

 dlls/wined3d/glsl_shader.c |    8 +++++---
 1 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/dlls/wined3d/glsl_shader.c b/dlls/wined3d/glsl_shader.c
index a59e54b..c4e4188 100644
--- a/dlls/wined3d/glsl_shader.c
+++ b/dlls/wined3d/glsl_shader.c
@@ -2314,16 +2314,18 @@ static void shader_glsl_nrm(const struct wined3d_shader_instruction *ins)
     mask_size = shader_glsl_get_write_mask_size(write_mask);
     shader_glsl_add_src_param(ins, &ins->src[0], write_mask, &src_param);
 
-    shader_addline(buffer, "tmp0.x = length(%s);\n", src_param.param_str);
+    shader_addline(buffer, "tmp0.x = dot(%s, %s);\n",
+            src_param.param_str, src_param.param_str);
     shader_glsl_append_dst(buffer, ins);
+
     if (mask_size > 1)
     {
-        shader_addline(buffer, "tmp0.x == 0.0 ? vec%u(0.0) : (%s / tmp0.x));\n",
+        shader_addline(buffer, "tmp0.x == 0.0 ? vec%u(0.0) : (%s * inversesqrt(tmp0.x)));\n",
                 mask_size, src_param.param_str);
     }
     else
     {
-        shader_addline(buffer, "tmp0.x == 0.0 ? 0.0 : (%s / tmp0.x));\n",
+        shader_addline(buffer, "tmp0.x == 0.0 ? 0.0 : (%s * inversesqrt(tmp0.x)));\n",
                 src_param.param_str);
     }
 }