DrawManager: Add Edge Detection To DisplayLists

Objects that internally uses DispList do not cast shadow in the workbench.
Their outline is also not visible in object mode. The reason for this is
that edge detection was not implemented for Display Lists. This patch will
implement the edge detection.

Reviewed By: fclem

Maniphest Tasks: T62479

Differential Revision: https://developer.blender.org/D4605

1 files changed, 95 insertions, 0 deletions

diff --git a/source/blender/draw/intern/draw_cache_impl_displist.c b/source/blender/draw/intern/draw_cache_impl_displist.c
index 63514acf1c2..dfac50e084c 100644
--- a/source/blender/draw/intern/draw_cache_impl_displist.c
+++ b/source/blender/draw/intern/draw_cache_impl_displist.c
@@ -28,6 +28,7 @@
 
 #include "BLI_alloca.h"
 #include "BLI_utildefines.h"
+#include "BLI_edgehash.h"
 #include "BLI_math_vector.h"
 
 #include "DNA_curve_types.h"
@@ -561,3 +562,97 @@ void DRW_displist_vertbuf_create_loop_pos_and_nor_and_uv(
 		}
 	}
 }
+
+/* Edge detection/adjecency */
+#define NO_EDGE INT_MAX
+static void set_edge_adjacency_lines_indices(EdgeHash *eh, GPUIndexBufBuilder *elb, bool *r_is_manifold, uint v1, uint v2, uint v3)
+{
+	bool inv_indices = (v2 > v3);
+	void **pval;
+	bool value_is_init = BLI_edgehash_ensure_p(eh, v2, v3, &pval);
+	int v_data = POINTER_AS_INT(*pval);
+	if (!value_is_init || v_data == NO_EDGE) {
+		/* Save the winding order inside the sign bit. Because the
+		 * edgehash sort the keys and we need to compare winding later. */
+		int value = (int)v1 + 1; /* Int 0 bm_looptricannot be signed */
+		*pval = POINTER_FROM_INT((inv_indices) ? -value : value);
+	}
+	else {
+		/* HACK Tag as not used. Prevent overhead of BLI_edgehash_remove. */
+		*pval = POINTER_FROM_INT(NO_EDGE);
+		bool inv_opposite = (v_data < 0);
+		uint v_opposite = (uint)abs(v_data) - 1;
+
+		if (inv_opposite == inv_indices) {
+			/* Don't share edge if triangles have non matching winding. */
+			GPU_indexbuf_add_line_adj_verts(elb, v1, v2, v3, v1);
+			GPU_indexbuf_add_line_adj_verts(elb, v_opposite, v2, v3, v_opposite);
+			*r_is_manifold = false;
+		}
+		else {
+			GPU_indexbuf_add_line_adj_verts(elb, v1, v2, v3, v_opposite);
+		}
+	}
+}
+
+static void set_edges_adjacency_lines_indices(void *thunk, uint v1, uint v2, uint v3)
+{
+	void **packed = (void**)thunk;
+	GPUIndexBufBuilder *elb = (GPUIndexBufBuilder*)packed[0];
+	EdgeHash *eh = (EdgeHash*)packed[1];
+	bool *r_is_manifold = (bool*)packed[2];
+
+	set_edge_adjacency_lines_indices(eh, elb, r_is_manifold, v1, v2, v3);
+	set_edge_adjacency_lines_indices(eh, elb, r_is_manifold, v2, v3, v1);
+	set_edge_adjacency_lines_indices(eh, elb, r_is_manifold, v3, v1, v2);
+}
+
+void DRW_displist_indexbuf_create_edges_adjacency_lines(struct ListBase *lb, struct GPUIndexBuf *ibo, bool *r_is_manifold)
+{
+	const int tri_len = curve_render_surface_tri_len_get(lb);
+	const int vert_len = curve_render_surface_vert_len_get(lb);
+
+	*r_is_manifold = true;
+
+	/* Allocate max but only used indices are sent to GPU. */
+	GPUIndexBufBuilder elb;
+	GPU_indexbuf_init(&elb, GPU_PRIM_LINES_ADJ, tri_len * 3, vert_len);
+
+	EdgeHash *eh = BLI_edgehash_new_ex(__func__, tri_len * 3);
+
+	/* pack values to pass to `set_edges_adjacency_lines_indices` function. */
+	void* thunk[3] = {&elb,eh, r_is_manifold};
+	int v_idx = 0;
+	for (const DispList *dl = lb->first; dl; dl = dl->next) {
+		displist_indexbufbuilder_set(
+		        (SetTriIndicesFn *)set_edges_adjacency_lines_indices,
+		        (SetTriIndicesFn *)set_edges_adjacency_lines_indices,
+		        thunk, dl, v_idx);
+		v_idx += dl_vert_len(dl);
+	}
+
+	/* Create edges for remaning non manifold edges. */
+	EdgeHashIterator *ehi;
+	for (ehi = BLI_edgehashIterator_new(eh);
+	     BLI_edgehashIterator_isDone(ehi) == false;
+	     BLI_edgehashIterator_step(ehi))
+	{
+		uint v1, v2;
+		int v_data = POINTER_AS_INT(BLI_edgehashIterator_getValue(ehi));
+		if (v_data == NO_EDGE) {
+			continue;
+		}
+		BLI_edgehashIterator_getKey(ehi, &v1, &v2);
+		uint v0 = (uint)abs(v_data) - 1;
+		if (v_data < 0) { /* inv_opposite  */
+			SWAP(uint, v1, v2);
+		}
+		GPU_indexbuf_add_line_adj_verts(&elb, v0, v1, v2, v0);
+		*r_is_manifold = false;
+	}
+	BLI_edgehashIterator_free(ehi);
+	BLI_edgehash_free(eh, NULL);
+
+	GPU_indexbuf_build_in_place(&elb, ibo);
+}
+#undef NO_EDGE