1 files changed, 300 insertions, 0 deletions
diff --git a/src/intersect.cu b/src/intersect.cu
new file mode 100644
index 0000000..1402aa1
--- /dev/null
+++ b/src/intersect.cu
@@ -0,0 +1,300 @@
+//-*-c-*-
+#include <math_constants.h>
+
+#include "linalg.h"
+#include "matrix.h"
+#include "rotate.h"
+
+/* flattened triangle mesh */
+texture<float4, 1, cudaReadModeElementType> mesh;
+
+/* lower/upper bounds for the bounding box associated with each node/leaf */
+texture<float4, 1, cudaReadModeElementType> upper_bound_arr;
+texture<float4, 1, cudaReadModeElementType> lower_bound_arr;
+
+/* map to child nodes/triangles and the number of child nodes/triangles */
+texture<uint, 1, cudaReadModeElementType> child_map_arr;
+texture<uint, 1, cudaReadModeElementType> child_len_arr;
+
+__device__ float3 make_float3(const float4 &a)
+{
+	return make_float3(a.x, a.y, a.z);
+}
+
+/* Test the intersection between a ray starting from `origin` traveling in the
+   direction `direction` and a triangle defined by the vertices `v0`, `v1`, and
+   `v2`. If the ray intersects the triangle, set `distance` to the distance
+   between `origin` and the intersection and return true, else return false.
+
+   `direction` must be normalized. */
+__device__ bool intersect_triangle(const float3 &origin, const float3 &direction, const float3 &v0, const float3 &v1, const float3 &v2, float &distance)
+{
+	Matrix m = make_matrix(v1-v0, v2-v0, -direction);
+	
+	float determinant = det(m);
+
+	if (determinant == 0.0f)
+		return false;
+
+	float3 b = origin-v0;
+
+	float u1 = ((m.a11*m.a22 - m.a12*m.a21)*b.x +
+		    (m.a02*m.a21 - m.a01*m.a22)*b.y +
+		    (m.a01*m.a12 - m.a02*m.a11)*b.z)/determinant;
+
+	if (u1 < 0.0f)
+		return false;
+
+	float u2 = ((m.a12*m.a20 - m.a10*m.a22)*b.x +
+		    (m.a00*m.a22 - m.a02*m.a20)*b.y +
+		    (m.a02*m.a10 - m.a00*m.a12)*b.z)/determinant;
+
+	if (u2 < 0.0f)
+		return false;
+
+	float u3 = ((m.a10*m.a21 - m.a11*m.a20)*b.x +
+		    (m.a01*m.a20 - m.a00*m.a21)*b.y +
+		    (m.a00*m.a11 - m.a01*m.a10)*b.z)/determinant;
+
+	if (u3 < 0.0f || (1-u1-u2) < 0.0f)
+		return false;
+
+	distance = u3;
+
+	return true;
+}
+
+/* Return the 32 bit color associated with the intersection between a ray
+   starting from `origin` traveling in the direction `direction` and the
+   plane defined by the points `v0`, `v1`, and `v2` using the cosine of the
+   angle between the ray and the plane normal to determine the brightness.
+
+   `direction` must be normalized. */
+__device__ int get_color(const float3 &direction, const float3 &v0, const float3& v1, const float3 &v2)
+{
+	float scale = 255*dot(normalize(cross(v1-v0,v2-v0)),-direction);
+
+	if (scale < 0.0f)
+		scale = 255*dot(-normalize(cross(v1-v0,v2-v0)),-direction);
+
+	int rgb = floorf(scale);
+
+	return rgb << 16 | rgb << 8 | rgb;
+}
+
+/* Test the intersection between a ray starting from `origin` traveling in the
+   direction `direction` and the axis-aligned box defined by the opposite
+   vertices `lower_bound` and `upper_bound`. If the ray intersects the box
+   return True, else return False. */
+__device__ bool intersect_box(const float3 &origin, const float3 &direction, const float3 &lower_bound, const float3 &upper_bound)
+{
+	float kmin, kmax, kymin, kymax, kzmin, kzmax;
+
+	if (direction.x >= 0.0f)
+	{
+		kmin = (lower_bound.x - origin.x)/direction.x;
+		kmax = (upper_bound.x - origin.x)/direction.x;
+	}
+	else
+	{
+		kmin = (upper_bound.x - origin.x)/direction.x;
+		kmax = (lower_bound.x - origin.x)/direction.x;
+	}
+
+	if (kmax < kmin)
+		return false;
+
+	if (direction.y >= 0.0f)
+	{
+		kymin = (lower_bound.y - origin.y)/direction.y;
+		kymax = (upper_bound.y - origin.y)/direction.y;
+	}
+	else
+	{
+		kymin = (upper_bound.y - origin.y)/direction.y;
+		kymax = (lower_bound.y - origin.y)/direction.y;
+	}
+
+	if (kymax < kymin)
+		return false;
+
+	if (kymin > kmin)
+		kmin = kymin;
+
+	if (kymax < kmax)
+		kmax = kymax;
+
+	if (kmin > kmax)
+		return false;
+
+	if (direction.z >= 0.0f)
+	{
+		kzmin = (lower_bound.z - origin.z)/direction.z;
+		kzmax = (upper_bound.z - origin.z)/direction.z;
+	}
+	else
+	{
+		kzmin = (upper_bound.z - origin.z)/direction.z;
+		kzmax = (lower_bound.z - origin.z)/direction.z;
+	}
+
+	if (kzmax < kzmin)
+		return false;
+
+	if (kzmin > kmin)
+		kmin = kzmin;
+
+	if (kzmax < kmax)
+		kmax = kzmax;
+
+	if (kmin > kmax)
+		return false;
+
+	if (kmax < 0.0f)
+		return false;
+
+	return true;
+}
+
+/* Test the intersection between a ray starting at `origin` traveling in the
+   direction `direction` and the bounding box around node `i`. If the ray
+   intersects the bounding box return true, else return false. */
+__device__ bool intersect_node(const float3 &origin, const float3 &direction, const int &i)
+{
+	float3 lower_bound = make_float3(tex1Dfetch(lower_bound_arr, i));
+	float3 upper_bound = make_float3(tex1Dfetch(upper_bound_arr, i));
+
+	return intersect_box(origin, direction, lower_bound, upper_bound);
+}
+
+extern "C"
+{
+
+__global__ void translate(int max_idx, float3 *pt, float3 v)
+{
+	int idx = blockIdx.x*blockDim.x + threadIdx.x;
+
+	if (idx > max_idx)
+		return;
+
+	pt[idx] += v;
+}
+
+__global__ void rotate(int max_idx, float3 *pt, float phi, float3 axis)
+{
+	int idx = blockIdx.x*blockDim.x + threadIdx.x;
+
+	if (idx > max_idx)
+		return;
+
+	pt[idx] = rotate(pt[idx], phi, axis);
+}
+
+__global__ void intersect_mesh(int max_idx, float3 *origin_arr, float3 *direction_arr, int first_leaf, int *state_arr, int *pixel_arr)
+{
+	int idx = blockIdx.x*blockDim.x + threadIdx.x;
+
+	if (idx > max_idx)
+		return;
+
+	float3 origin = origin_arr[idx];
+	float3 direction = direction_arr[idx];
+	direction /= norm(direction);
+
+	int *pixel = pixel_arr+idx;
+	int *state = state_arr+idx;
+
+	bool hit = false;
+
+	float distance;
+	float min_distance;
+	
+	if (!intersect_node(origin, direction, 0))
+	{
+		*pixel = 0;
+		return;
+	}
+
+	int stack[100];
+
+	int *head = &stack[0];
+	int *node = &stack[1];
+	*node = 0;
+
+	int i;
+
+	bool show_leafs = false;
+
+	do
+	{
+		int child_map = tex1Dfetch(child_map_arr, *node);
+		int child_len = tex1Dfetch(child_len_arr, *node);
+
+		if (*node < first_leaf)
+		{
+			for (i=0; i < child_len; i++)
+				if (intersect_node(origin, direction, child_map+i))
+					*node++ = child_map+i;
+
+			if (node == head)
+				break;
+			
+			node--;
+
+		}
+		else if (show_leafs)
+		{
+			hit = true;
+			*pixel = 255;
+			node--;
+		}
+		else // node is a leaf
+		{
+			for (i=0; i < child_len; i++)
+			{
+				int mesh_idx = 3*(child_map + i);
+
+				float3 v0 = make_float3(tex1Dfetch(mesh, mesh_idx));
+				float3 v1 = make_float3(tex1Dfetch(mesh, mesh_idx+1));
+				float3 v2 = make_float3(tex1Dfetch(mesh, mesh_idx+2));
+				
+				if (intersect_triangle(origin, direction, v0, v1, v2, distance))
+				{
+					if (!hit)
+					{
+						*pixel = get_color(direction, v0, v1, v2);
+						*state = child_map + i;
+
+						min_distance = distance;
+
+						hit = true;
+						continue;
+					}
+					
+					if (distance < min_distance)
+					{
+						*pixel = get_color(direction, v0, v1, v2);
+						*state = child_map + i;
+						
+						min_distance = distance;
+					}
+				}
+
+			} // triangle loop
+
+			node--;
+
+		} // node is a leaf
+
+	} // while loop
+	while (node != head);
+
+	if (!hit)
+	{
+		*state = -1;
+		*pixel = 0;
+	}
+
+} // intersect mesh
+
+} // extern "c"