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.

wined3d: Use dot() instead of length() in shader_glsl_nrm().
a50546e5 · Henri Verbeet · Alexandre Julliard · 010e285b · a50546e5
Commit a50546e5 authored Jan 24, 2011 by Henri Verbeet Committed by Alexandre Julliard Jan 24, 2011
Hide whitespace changes
Inline Side-by-side

Showing with 5 additions and 3 deletions

glsl_shader.c dlls/wined3d/glsl_shader.c +5 -3

No files found.
--- 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);
    }
 }