blender/intern/cycles/bvh/bvh_params.h

/*
 * Adapted from code copyright 2009-2010 NVIDIA Corporation
 * Modifications Copyright 2011, Blender Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef __BVH_PARAMS_H__
#define __BVH_PARAMS_H__

#include "util_boundbox.h"

#include "kernel_types.h"

CCL_NAMESPACE_BEGIN

/* BVH Parameters */

class BVHParams
{
public:
	/* spatial split area threshold */
	bool use_spatial_split;
	float spatial_split_alpha;

	/* Unaligned nodes creation threshold */
	float unaligned_split_threshold;

	/* SAH costs */
	float sah_node_cost;
	float sah_primitive_cost;

	/* number of primitives in leaf */
	int min_leaf_size;
	int max_triangle_leaf_size;
	int max_motion_triangle_leaf_size;
	int max_curve_leaf_size;
	int max_motion_curve_leaf_size;

	/* object or mesh level bvh */
	bool top_level;

	/* QBVH */
	bool use_qbvh;

	/* Mask of primitives to be included into the BVH. */
	int primitive_mask;

	/* Use unaligned bounding boxes.
	 * Only used for curves BVH.
	 */
	bool use_unaligned_nodes;

	/* Split time range to this number of steps and create leaf node for each
	 * of this time steps.
	 *
	 * Speeds up rendering of motion curve primitives in the cost of higher
	 * memory usage.
	 */
	int num_motion_curve_steps;

	/* Same as above, but for triangle primitives. */
	int num_motion_triangle_steps;

	/* fixed parameters */
	enum {
		MAX_DEPTH = 64,
		MAX_SPATIAL_DEPTH = 48,
		NUM_SPATIAL_BINS = 32
	};

	BVHParams()
	{
		use_spatial_split = true;
		spatial_split_alpha = 1e-5f;

		unaligned_split_threshold = 0.7f;

		/* todo: see if splitting up primitive cost to be separate for triangles
		 * and curves can help. so far in tests it doesn't help, but why? */
		sah_node_cost = 1.0f;
		sah_primitive_cost = 1.0f;

		min_leaf_size = 1;
		max_triangle_leaf_size = 8;
		max_motion_triangle_leaf_size = 8;
		max_curve_leaf_size = 1;
		max_motion_curve_leaf_size = 4;

		top_level = false;
		use_qbvh = false;
		use_unaligned_nodes = false;

		primitive_mask = PRIMITIVE_ALL;

		num_motion_curve_steps = 0;
	}

	/* SAH costs */
	__forceinline float cost(int num_nodes, int num_primitives) const
	{ return node_cost(num_nodes) + primitive_cost(num_primitives); }

	__forceinline float primitive_cost(int n) const
	{ return n*sah_primitive_cost; }

	__forceinline float node_cost(int n) const
	{ return n*sah_node_cost; }

	__forceinline bool small_enough_for_leaf(int size, int level)
	{ return (size <= min_leaf_size || level >= MAX_DEPTH); }
};

/* BVH Reference
 *
 * Reference to a primitive. Primitive index and object are sneakily packed
 * into BoundBox to reduce memory usage and align nicely */

class BVHReference
{
public:
	__forceinline BVHReference() {}

	__forceinline BVHReference(const BoundBox& bounds_,
	                           int prim_index_,
	                           int prim_object_,
	                           int prim_type,
	                           float time_from = 0.0f,
	                           float time_to = 1.0f)
	        : rbounds(bounds_),
	          time_from_(time_from),
	          time_to_(time_to)
	{
		rbounds.min.w = __int_as_float(prim_index_);
		rbounds.max.w = __int_as_float(prim_object_);
		type = prim_type;
	}

	__forceinline const BoundBox& bounds() const { return rbounds; }
	__forceinline int prim_index() const { return __float_as_int(rbounds.min.w); }
	__forceinline int prim_object() const { return __float_as_int(rbounds.max.w); }
	__forceinline int prim_type() const { return type; }
	__forceinline float time_from() const { return time_from_; }
	__forceinline float time_to() const { return time_to_; }


	BVHReference& operator=(const BVHReference &arg) {
		if(&arg != this) {
			memcpy(this, &arg, sizeof(BVHReference));
		}
		return *this;
	}


protected:
	BoundBox rbounds;
	uint type;
	float time_from_, time_to_;
};

/* BVH Range
 *
 * Build range used during construction, to indicate the bounds and place in
 * the reference array of a subset of primitives Again uses trickery to pack
 * integers into BoundBox for alignment purposes. */

class BVHRange
{
public:
	__forceinline BVHRange()
	{
		rbounds.min.w = __int_as_float(0);
		rbounds.max.w = __int_as_float(0);
	}

	__forceinline BVHRange(const BoundBox& bounds_, int start_, int size_)
	: rbounds(bounds_)
	{
		rbounds.min.w = __int_as_float(start_);
		rbounds.max.w = __int_as_float(size_);
	}

	__forceinline BVHRange(const BoundBox& bounds_, const BoundBox& cbounds_, int start_, int size_)
	: rbounds(bounds_), cbounds(cbounds_)
	{
		rbounds.min.w = __int_as_float(start_);
		rbounds.max.w = __int_as_float(size_);
	}

	__forceinline void set_start(int start_) { rbounds.min.w = __int_as_float(start_); }

	__forceinline const BoundBox& bounds() const { return rbounds; }
	__forceinline const BoundBox& cent_bounds() const { return cbounds; }
	__forceinline int start() const { return __float_as_int(rbounds.min.w); }
	__forceinline int size() const { return __float_as_int(rbounds.max.w); }
	__forceinline int end() const { return start() + size(); }

protected:
	BoundBox rbounds;
	BoundBox cbounds;
};

/* BVH Spatial Bin */

struct BVHSpatialBin
{
	BoundBox bounds;
	int enter;
	int exit;

	__forceinline BVHSpatialBin()
	{
	}
};

/* BVH Spatial Storage
 *
 * The idea of this storage is have thread-specific storage for the spatial
 * splitters. We can pre-allocate this storage in advance and avoid heavy memory
 * operations during split process.
 */

struct BVHSpatialStorage {
	/* Accumulated bounds when sweeping from right to left.  */
	vector<BoundBox> right_bounds;

	/* Bins used for histogram when selecting best split plane. */
	BVHSpatialBin bins[3][BVHParams::NUM_SPATIAL_BINS];

	/* Temporary storage for the new references. Used by spatial split to store
	 * new references in before they're getting inserted into actual array,
	 */
	vector<BVHReference> new_references;
};

CCL_NAMESPACE_END

#endif /* __BVH_PARAMS_H__ */