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authorIan Romanick <ian.d.romanick@intel.com>2008-12-18 14:11:06 -0800
committerIan Romanick <ian.d.romanick@intel.com>2008-12-19 13:06:53 -0800
commit962fa6bbc16abf2b9829bd0b761d9baa9d01fd1e (patch)
treed3e42f5a82b98f435a573550f45566bf686b8890
parent1db63713046efd49071aae448105df8a80e1e83d (diff)
GLSL: The LOG2 macro doesn't have enough precision
It looks like the LOG2 macro only has 8 or 9 bits of precission, but the ARB_vertex_program spec says "accurate to at least 10 bits".
-rw-r--r--src/mesa/shader/prog_execute.c11
1 files changed, 9 insertions, 2 deletions
diff --git a/src/mesa/shader/prog_execute.c b/src/mesa/shader/prog_execute.c
index 8163ae6a6f..a93733c085 100644
--- a/src/mesa/shader/prog_execute.c
+++ b/src/mesa/shader/prog_execute.c
@@ -963,7 +963,10 @@ _mesa_execute_program(GLcontext * ctx,
{
GLfloat a[4], result[4];
fetch_vector1(&inst->SrcReg[0], machine, a);
- result[0] = result[1] = result[2] = result[3] = LOG2(a[0]);
+ /* The fast LOG2 macro doesn't meet the precision requirements.
+ */
+ result[0] = result[1] = result[2] = result[3] =
+ (log(a[0]) * 1.442695F);
store_vector4(inst, machine, result);
}
break;
@@ -1022,7 +1025,11 @@ _mesa_execute_program(GLcontext * ctx,
GLfloat mantissa = FREXPF(t[0], &exponent);
q[0] = (GLfloat) (exponent - 1);
q[1] = (GLfloat) (2.0 * mantissa); /* map [.5, 1) -> [1, 2) */
- q[2] = (GLfloat) (q[0] + LOG2(q[1]));
+
+ /* The fast LOG2 macro doesn't meet the precision
+ * requirements.
+ */
+ q[2] = (log(t[0]) * 1.442695F);
}
}
else {