Batch kernels for forward pass of Preprocessing

.gitignore

@@ -3,3 +3,4 @@ diff_gaussian_rasterization.egg-info/
 dist/
 diff_gaussian_rasterization/__pycache__/
 *so
+*.pyc

cuda_rasterizer/forward.cu

@@ -18,16 +18,16 @@ namespace cg = cooperative_groups;
 
 // Forward method for converting the input spherical harmonics
 // coefficients of each Gaussian to a simple RGB color.
-__device__ glm::vec3 computeColorFromSH(int idx, int deg, int max_coeffs, const glm::vec3* means, glm::vec3 campos, const float* shs, bool* clamped)
+__device__ glm::vec3 computeColorFromSH(int point_idx, int result_idx, int deg, int max_coeffs, const glm::vec3* means, glm::vec3 campos, const float* shs, bool* clamped)
 {
 	// The implementation is loosely based on code for 
 	// "Differentiable Point-Based Radiance Fields for 
 	// Efficient View Synthesis" by Zhang et al. (2022)
-	glm::vec3 pos = means[idx];
+	glm::vec3 pos = means[point_idx];
 	glm::vec3 dir = pos - campos;
 	dir = dir / glm::length(dir);
 
-	glm::vec3* sh = ((glm::vec3*)shs) + idx * max_coeffs;
+	glm::vec3* sh = ((glm::vec3*)shs) + point_idx * max_coeffs;
 	glm::vec3 result = SH_C0 * sh[0];
 
 	if (deg > 0)
@@ -65,9 +65,9 @@ __device__ glm::vec3 computeColorFromSH(int idx, int deg, int max_coeffs, const
 
 	// RGB colors are clamped to positive values. If values are
 	// clamped, we need to keep track of this for the backward pass.
-	clamped[3 * idx + 0] = (result.x < 0);
-	clamped[3 * idx + 1] = (result.y < 0);
-	clamped[3 * idx + 2] = (result.z < 0);
+	clamped[3 * result_idx + 0] = (result.x < 0);
+	clamped[3 * result_idx + 1] = (result.y < 0);
+	clamped[3 * result_idx + 2] = (result.z < 0);
 	return glm::max(result, 0.0f);
 }
 
@@ -213,7 +213,6 @@ __global__ void preprocessCUDA(int P, int D, int M,
 		computeCov3D(scales[idx], scale_modifier, rotations[idx], cov3Ds + idx * 6);
 		cov3D = cov3Ds + idx * 6;
 	}
-
 	// Compute 2D screen-space covariance matrix
 	float3 cov = computeCov2D(p_orig, focal_x, focal_y, tan_fovx, tan_fovy, cov3D, viewmatrix);
 
@@ -242,7 +241,7 @@ __global__ void preprocessCUDA(int P, int D, int M,
 	// spherical harmonics coefficients to RGB color.
 	if (colors_precomp == nullptr)
 	{
-		glm::vec3 result = computeColorFromSH(idx, D, M, (glm::vec3*)orig_points, *cam_pos, shs, clamped);
+		glm::vec3 result = computeColorFromSH(idx, idx, D, M, (glm::vec3*)orig_points, *cam_pos, shs, clamped);
 		rgb[idx * C + 0] = result.x;
 		rgb[idx * C + 1] = result.y;
 		rgb[idx * C + 2] = result.z;
@@ -471,7 +470,7 @@ void FORWARD::preprocess(int P, int D, int M,
 	uint32_t* tiles_touched,
 	bool prefiltered)
 {
-	preprocessCUDA<NUM_CHANNELS> << <(P + ONE_DIM_BLOCK_SIZE - 1) / ONE_DIM_BLOCK_SIZE, ONE_DIM_BLOCK_SIZE >> > (
+	preprocessCUDA<NUM_CHANNELS> << <cdiv(P, ONE_DIM_BLOCK_SIZE), ONE_DIM_BLOCK_SIZE >> > (
 		P, D, M,
 		means3D,
 		scales,
@@ -498,4 +497,155 @@ void FORWARD::preprocess(int P, int D, int M,
 		tiles_touched,
 		prefiltered
 		);
-}
+}
+
+
+template<int C>
+__global__ void preprocessCUDABatched(
+    int P, int D, int M,
+    const float* orig_points, const glm::vec3* scales, const float scale_modifier,
+    const glm::vec4* rotations, const float* opacities, const float* shs,
+    bool* clamped, const float* cov3D_precomp, const float* colors_precomp,
+    const float* viewmatrix_arr, const float* projmatrix_arr, const glm::vec3* cam_pos,
+    const int W, int H, const float* tan_fovx, const float* tan_fovy,
+    int* radii, float2* points_xy_image, float* depths, float* cov3Ds,
+    float* rgb, float4* conic_opacity, const dim3 grid, uint32_t* tiles_touched,
+    bool prefiltered, const int num_viewpoints)
+{
+    auto point_idx = blockIdx.x * blockDim.x + threadIdx.x;
+    auto viewpoint_idx = blockIdx.y;
+
+    if (viewpoint_idx >= num_viewpoints || point_idx >= P) return;
+
+    auto idx = viewpoint_idx * P + point_idx;
+    const float* viewmatrix = viewmatrix_arr + viewpoint_idx * 16;
+    const float* projmatrix = projmatrix_arr + viewpoint_idx * 16;
+
+    // Initialize radius and touched tiles to 0. If this isn't changed,
+    // this Gaussian will not be processed further.
+    radii[idx] = 0;
+    tiles_touched[idx] = 0;
+
+    // Perform near culling, quit if outside.
+    float3 p_view;
+    if (!in_frustum(point_idx, orig_points, viewmatrix, projmatrix, prefiltered, p_view)) return;
+
+    // Transform point by projecting
+    float3 p_orig = { orig_points[3 * point_idx], orig_points[3 * point_idx + 1], orig_points[3 * point_idx + 2] };
+
+    float4 p_hom = transformPoint4x4(p_orig, projmatrix);
+    float p_w = 1.0f / (p_hom.w + 0.0000001f);
+    float3 p_proj = { p_hom.x * p_w, p_hom.y * p_w, p_hom.z * p_w };
+
+    // If 3D covariance matrix is precomputed, use it, otherwise compute
+    // from scaling and rotation parameters.
+    const float* cov3D;
+    if (cov3D_precomp != nullptr) {
+        cov3D = cov3D_precomp + idx * 6;
+    } else {
+        computeCov3D(scales[point_idx], scale_modifier, rotations[point_idx], cov3Ds + idx * 6);
+        cov3D = cov3Ds + idx * 6;
+    }
+
+
+    // Compute 2D screen-space covariance matrix
+    const float focal_x = W / (2.0f * tan_fovx[viewpoint_idx]);
+    const float focal_y = H / (2.0f * tan_fovy[viewpoint_idx]);
+    float3 cov = computeCov2D(p_orig, focal_x, focal_y, tan_fovx[viewpoint_idx], tan_fovy[viewpoint_idx], cov3D, viewmatrix);
+
+
+    // Invert covariance (EWA algorithm)
+    float det = (cov.x * cov.z - cov.y * cov.y);
+    if (det == 0.0f) return;
+    float det_inv = 1.f / det;
+    float3 conic = { cov.z * det_inv, -cov.y * det_inv, cov.x * det_inv };
+
+    // Compute extent in screen space (by finding eigenvalues of
+    // 2D covariance matrix). Use extent to compute a bounding rectangle
+    // of screen-space tiles that this Gaussian overlaps with. Quit if
+    // rectangle covers 0 tiles.
+    float mid = 0.5f * (cov.x + cov.z);
+    float lambda1 = mid + sqrt(max(0.1f, mid * mid - det));
+    float lambda2 = mid - sqrt(max(0.1f, mid * mid - det));
+    float my_radius = ceil(3.f * sqrt(max(lambda1, lambda2)));
+    float2 point_image = { ndc2Pix(p_proj.x, W), ndc2Pix(p_proj.y, H) };
+    uint2 rect_min, rect_max;
+    getRect(point_image, my_radius, rect_min, rect_max, grid);
+    if ((rect_max.x - rect_min.x) * (rect_max.y - rect_min.y) == 0) return;
+
+    // If colors have been precomputed, use them, otherwise convert
+    // spherical harmonics coefficients to RGB color.
+
+    if (colors_precomp == nullptr) {
+
+        glm::vec3 result = computeColorFromSH(point_idx, idx, D, M, (glm::vec3*)orig_points, cam_pos[viewpoint_idx], shs, clamped);
+        rgb[idx * C + 0] = result.x;
+        rgb[idx * C + 1] = result.y;
+        rgb[idx * C + 2] = result.z;
+    }
+
+    // Store some useful helper data for the next steps.
+    depths[idx] = p_view.z;
+    radii[idx] = my_radius;
+    points_xy_image[idx] = point_image;
+
+    // Inverse 2D covariance and opacity neatly pack into one float4
+    conic_opacity[idx] = { conic.x, conic.y, conic.z, opacities[point_idx] };
+    tiles_touched[idx] = (rect_max.y - rect_min.y) * (rect_max.x - rect_min.x);
+}
+
+void FORWARD::preprocess_batch(int P, int D, int M,
+	const float* means3D,
+	const glm::vec3* scales,
+	const float scale_modifier,
+	const glm::vec4* rotations,
+	const float* opacities,
+	const float* shs,
+	bool* clamped,
+	const float* cov3D_precomp,
+	const float* colors_precomp,
+	const float* viewmatrix,
+	const float* projmatrix,
+	const glm::vec3* cam_pos,
+	const int W, int H,
+	const float* tan_fovx, const float* tan_fovy,
+	int* radii,
+	float2* means2D,
+	float* depths,
+	float* cov3Ds,
+	float* rgb,
+	float4* conic_opacity,
+	const dim3 grid,
+	uint32_t* tiles_touched,
+	bool prefiltered,
+    const int num_viewpoints)
+{
+    dim3 tile_grid(cdiv(P, ONE_DIM_BLOCK_SIZE), num_viewpoints);
+    preprocessCUDABatched<NUM_CHANNELS><<<tile_grid, ONE_DIM_BLOCK_SIZE>>>(
+		P, D, M,
+		means3D,
+		scales,
+		scale_modifier,
+		rotations,
+		opacities,
+		shs,
+		clamped,
+		cov3D_precomp,
+		colors_precomp,
+		viewmatrix, 
+		projmatrix,
+		cam_pos,
+		W, H,
+		tan_fovx, tan_fovy,
+		radii,
+		means2D,
+		depths,
+		cov3Ds,
+		rgb,
+		conic_opacity,
+		grid,
+		tiles_touched,
+		prefiltered,
+		num_viewpoints
+		);
+}

cuda_rasterizer/forward.h

@@ -45,7 +45,35 @@ namespace FORWARD
 		float4* conic_opacity,
 		const dim3 grid,
 		uint32_t* tiles_touched,
-		bool prefiltered);
+		bool prefiltered
+    );
+
+    void preprocess_batch(int P, int D, int M,
+        const float* means3D,
+        const glm::vec3* scales,
+        const float scale_modifier,
+        const glm::vec4* rotations,
+        const float* opacities,
+        const float* shs,
+        bool* clamped,
+        const float* cov3D_precomp,
+        const float* colors_precomp,
+        const float* viewmatrix,
+        const float* projmatrix,
+        const glm::vec3* cam_pos,
+        const int W, int H,
+        const float* tan_fovx, const float* tan_fovy,
+        int* radii,
+        float2* means2D,
+        float* depths,
+        float* cov3Ds,
+        float* rgb,
+        float4* conic_opacity,
+        const dim3 grid,
+        uint32_t* tiles_touched,
+        bool prefiltered,
+        const int num_viewpoints
+    );
 
 	// Main rasterization method.
 	void render(
@@ -61,7 +89,8 @@ namespace FORWARD
 		uint32_t* n_contrib2loss,
         const int* compute_locally_1D_2D_map,
 		const float* bg_color,
-		float* out_color);
+		float* out_color
+    );
 }
 
 

cuda_rasterizer/rasterizer.h

@@ -65,6 +65,31 @@ namespace CudaRasterizer
 			bool debug,//raster_settings
 			const pybind11::dict &args);
 
+		static int preprocessForwardBatches(
+			float2* means2D,
+			float* depths,
+			int* radii,
+			float* cov3D,
+			float4* conic_opacity,
+			float* rgb,
+			bool* clamped,//the above are all per-Gaussian intemediate results.
+			const int P, int D, int M,
+			const int width, int height,
+			const float* means3D,
+			const float* scales,
+			const float* rotations,
+			const float* shs,
+			const float* opacities,//3dgs parameters
+			const float scale_modifier,
+			const float* viewmatrix,
+			const float* projmatrix,
+			const float* cam_pos,
+			const float* tan_fovx, const float* tan_fovy,
+			const bool prefiltered,
+			const int num_viewpoints,
+			bool debug,//raster_settings
+			const pybind11::dict &args);
+
 		static void preprocessBackward(
 			const int* radii,
 			const float* cov3D,