Commit: 68d41c95aed7a212edb3766ec85358daf294aec4
Author: Thomas Dinges
Date: Fri Jun 17 23:16:31 2016 +0200
Branches: soc-2016-cycles_images
https://developer.blender.org/rB68d41c95aed7a212edb3766ec85358daf294aec4
Add float to half conversion code, which can be used on CPU to convert float
textures slots to half.
Still need to hook these up with actual Image Manager.
===================================================================
M intern/cycles/util/util_half.h
===================================================================
diff --git a/intern/cycles/util/util_half.h b/intern/cycles/util/util_half.h
index 724c406..114cc55 100644
--- a/intern/cycles/util/util_half.h
+++ b/intern/cycles/util/util_half.h
@@ -38,11 +38,14 @@ struct half4 { half x, y, z, w; };
#endif
/* Float <-> Half conversion.
- * We define three main functions for each architecture.
- * Half data is always loaded / written via pointers.
+ * We define three main functions for each architecture:
* float4_store_half()
* half_to_float()
* half_to_float4()
+ *
+ * Additionally we have a function which only run on the CPU, and converts
float to half data,
+ * as used for textures.
+ * float_to_half()
*/
/* OpenCL */
@@ -139,6 +142,115 @@ ccl_device_inline float4 half4_to_float4(half4 h)
return f;
}
+#endif
+
+/* Float to half conversion, CPU only */
+#ifndef __KERNEL_GPU__
+
+/* Code from https://gist.github.com/rygorous/2156668, CC0 */
+union FP32
+{
+ uint u;
+ float f;
+ struct
+ {
+ uint Mantissa : 23;
+ uint Exponent : 8;
+ uint Sign : 1;
+ };
+};
+
+union FP16
+{
+ half u;
+ struct
+ {
+ uint Mantissa : 10;
+ uint Exponent : 5;
+ uint Sign : 1;
+ };
+};
+
+static FP16 float_to_half_fast(FP32 f)
+{
+ FP16 o = { 0 };
+
+ /* Based on ISPC reference code (with minor modifications) */
+ if(f.Exponent == 255) { /* Inf or NaN (all exponent bits set) */
+ o.Exponent = 31;
+ o.Mantissa = f.Mantissa ? 0x200 : 0; // NaN->qNaN and Inf->Inf
+ }
+ else { /* Normalized number */
+ /* Exponent unbias the single, then bias the halfp */
+ int newexp = f.Exponent - 127 + 15;
+
+ if(newexp >= 31) /* Overflow, return signed infinity */
+ o.Exponent = 31;
+ else if(newexp <= 0) { /* Underflow */
+ if((14 - newexp) <= 24) { /* Mantissa might be non-zero
*/
+ uint mant = f.Mantissa | 0x800000; /* Hidden 1
bit */
+ o.Mantissa = mant >> (14 - newexp);
+ if((mant >> (13 - newexp)) & 1) /* Check for
rounding */
+ o.u++; /* Round, might overflow into
exp bit, but this is OK */
+ }
+ }
+ else {
+ o.Exponent = newexp;
+ o.Mantissa = f.Mantissa >> 13;
+ if(f.Mantissa & 0x1000) /* Check for rounding */
+ o.u++; /* Round, might overflow to inf, this is
OK */
+ }
+ }
+
+ o.Sign = f.Sign;
+ return o;
+}
+
+static FP16 float_to_half_fast2(FP32 f)
+{
+ FP32 infty = { 31 << 23 };
+ FP32 magic = { 15 << 23 };
+ FP16 o = { 0 };
+
+ uint sign = f.Sign;
+ f.Sign = 0;
+
+ /* Based on ISPC reference code (with minor modifications) */
+ if(f.Exponent == 255) { /* Inf or NaN (all exponent bits set) */
+ o.Exponent = 31;
+ o.Mantissa = f.Mantissa ? 0x200 : 0; // NaN->qNaN and Inf->Inf
+ }
+ else { /* (De)normalized number or zero */
+ f.u &= ~0xfff; // Make sure we don't get sticky bits
+
+ f.f *= magic.f;
+
+ f.u += 0x1000; /* Rounding bias */
+ if(f.u > infty.u) f.u = infty.u; /* Clamp to signed infinity if
overflowed */
+
+ o.u = f.u >> 13; /* Take the bits! */
+ }
+
+ o.Sign = sign;
+ return o;
+}
+
+
+ccl_device_inline half float_to_half(float f)
+{
+ FP32 fp;
+ fp.f = f;
+
+ FP16 h = float_to_half_fast(fp);
+
+ return h.u;
+}
+
+ccl_device void print_half(float f)
+{
+ std::cout << "Float" << f << std::endl;
+ std::cout << "Half" << float_to_half(f) << std::endl;
+}
#endif
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