Cycles: combined CPU + GPU rendering support.

CPU rendering will be restricted to a BVH2, which is not ideal for raytracing
performance but can be shared with the GPU. Decoupled volume shading will be
disabled to match GPU volume sampling.

The number of CPU rendering threads is reduced to leave one core dedicated to
each GPU. Viewport rendering will also only use GPU rendering still. So along
with the BVH2 usage, perfect scaling should not be expected.

Go to User Preferences > System to enable the CPU to render alongside the GPU.

Differential Revision: https://developer.blender.org/D2873

1 files changed, 27 insertions, 5 deletions

diff --git a/intern/cycles/device/device.cpp b/intern/cycles/device/device.cpp
index 7b0875965f8..f31cacd8ec1 100644
--- a/intern/cycles/device/device.cpp
+++ b/intern/cycles/device/device.cpp
@@ -23,9 +23,11 @@
 #include "util/util_debug.h"
 #include "util/util_foreach.h"
 #include "util/util_half.h"
+#include "util/util_logging.h"
 #include "util/util_math.h"
 #include "util/util_opengl.h"
 #include "util/util_time.h"
+#include "util/util_system.h"
 #include "util/util_types.h"
 #include "util/util_vector.h"
 #include "util/util_string.h"
@@ -365,7 +367,7 @@ string Device::device_capabilities()
 	return capabilities;
 }
 
-DeviceInfo Device::get_multi_device(vector<DeviceInfo> subdevices)
+DeviceInfo Device::get_multi_device(const vector<DeviceInfo>& subdevices, int threads, bool background)
 {
 	assert(subdevices.size() > 1);
 
@@ -373,18 +375,38 @@ DeviceInfo Device::get_multi_device(vector<DeviceInfo> subdevices)
 	info.type = DEVICE_MULTI;
 	info.id = "MULTI";
 	info.description = "Multi Device";
-	info.multi_devices = subdevices;
 	info.num = 0;
 
 	info.has_bindless_textures = true;
 	info.has_volume_decoupled = true;
 	info.has_qbvh = true;
-	foreach(DeviceInfo &device, subdevices) {
-		assert(device.type == info.multi_devices[0].type);
-
+	foreach(const DeviceInfo &device, subdevices) {
 		info.has_bindless_textures &= device.has_bindless_textures;
 		info.has_volume_decoupled &= device.has_volume_decoupled;
 		info.has_qbvh &= device.has_qbvh;
+
+		if(device.type == DEVICE_CPU && subdevices.size() > 1) {
+			if(background) {
+				int orig_cpu_threads = (threads)? threads: system_cpu_thread_count();
+				int cpu_threads = max(orig_cpu_threads - (subdevices.size() - 1), 0);
+
+				if(cpu_threads >= 1) {
+					DeviceInfo cpu_device = device;
+					cpu_device.cpu_threads = cpu_threads;
+					info.multi_devices.push_back(cpu_device);
+				}
+
+				VLOG(1) << "CPU render threads reduced from "
+						<< orig_cpu_threads << " to " << cpu_threads
+						<< ", to dedicate to GPU.";
+			}
+			else {
+				VLOG(1) << "CPU render threads disabled for interactive render.";
+			}
+		}
+		else {
+			info.multi_devices.push_back(device);
+		}
 	}
 
 	return info;