From: Mikko Rasa <tdb@tdb.fi>
Date: Mon, 11 Oct 2021 13:05:16 +0000 (+0300)
Subject: Apply shadow depth bias in a different way
X-Git-Url: http://git.tdb.fi/?a=commitdiff_plain;h=b733c793381e78637f52c7f77cc4f69e914918e1;p=libs%2Fgl.git

Apply shadow depth bias in a different way

It cannot be properly applied through the matrix for perspective
projection.
---

diff --git a/shaderlib/shadow.glsl b/shaderlib/shadow.glsl
index 2fa1fd81..438af68d 100644
--- a/shaderlib/shadow.glsl
+++ b/shaderlib/shadow.glsl
@@ -6,6 +6,7 @@ struct ShadowParameters
 	float darkness;
 	int matrix_index;
 	vec4 region;
+	float bias;
 };
 
 uniform ShadowMap
@@ -26,7 +27,10 @@ virtual float get_shadow_factor(int index, vec4 world_pos)
 		int type = shadows[index].type;
 		vec3 shadow_coord;
 		if(type==1)
+		{
 			shadow_coord = (shd_world_matrix[shadows[index].matrix_index]*world_pos).xyz;
+			shadow_coord.z -= shadows[index].bias;
+		}
 		else
 			return 1.0;
 
@@ -34,7 +38,7 @@ virtual float get_shadow_factor(int index, vec4 world_pos)
 			return 1.0;
 
 		vec4 region = shadows[index].region;
-		float shadow_sample = texture(shadow_map, shadow_coord*vec3(region.zw, 1.0)+vec3(region.xy, 0.0));
+		float shadow_sample = texture(shadow_map, vec3(shadow_coord.xy*region.zw+region.xy, shadow_coord.z));
 		return mix(1.0, shadow_sample, shadows[index].darkness);
 	}
 	else
diff --git a/source/effects/shadowmap.cpp b/source/effects/shadowmap.cpp
index 4cc0475d..46524397 100644
--- a/source/effects/shadowmap.cpp
+++ b/source/effects/shadowmap.cpp
@@ -30,6 +30,7 @@ ShadowMap::ShadowMap(unsigned w, unsigned h, Renderable &r, const Lighting *l):
 		shdata.uniform(base+".darkness", 1.0f);
 		shdata.uniform(base+".matrix_index", 0);
 		shdata.uniform(base+".region", Vector4(0.0f, 0.0f, 1.0f, 1.0f));
+		shdata.uniform(base+".bias", 0.0f);
 	}
 
 	Matrix dummy_matrix;
@@ -160,6 +161,13 @@ void ShadowMap::setup_frame(Renderer &renderer)
 	for(const ShadowedLight &l: lights)
 		l.shadow_caster->setup_frame(renderer);
 
+	for(const ShadowedLight &l: lights)
+	{
+		string base = format("shadows[%d]", l.index);
+		if(l.type==DIRECTIONAL)
+			shdata.uniform(base+".bias", depth_bias/l.region.width);
+	}
+
 	vector<Matrix> shadow_matrices;
 	shadow_matrices.reserve(views.size());
 	for(ShadowView &v: views)
@@ -174,7 +182,7 @@ void ShadowMap::setup_frame(Renderer &renderer)
 			v.camera.set_depth_clip(-radius, radius);
 		}
 
-		Matrix to_texcoord = Matrix().translate(Vector3(0.5f, 0.5f, 0.5f-depth_bias/light.region.width)).scale(0.5f);
+		Matrix to_texcoord = Matrix().translate(Vector3(0.5f, 0.5f, 0.5f)).scale(0.5f);
 		shadow_matrices.push_back(to_texcoord*v.camera.get_projection_matrix()*v.camera.get_view_matrix());
 	}