diff options
| author | Ian Romanick <[email protected]> | 2008-12-18 14:11:06 -0800 |
|---|---|---|
| committer | Ian Romanick <[email protected]> | 2008-12-19 13:06:53 -0800 |
| commit | 962fa6bbc16abf2b9829bd0b761d9baa9d01fd1e (patch) | |
| tree | d3e42f5a82b98f435a573550f45566bf686b8890 | |
| parent | 1db63713046efd49071aae448105df8a80e1e83d (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.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/src/mesa/shader/prog_execute.c b/src/mesa/shader/prog_execute.c index 8163ae6a6f5..a93733c0852 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 { |