From: Mikko Rasa <tdb@tdb.fi>
Date: Tue, 30 Jul 2024 21:36:11 +0000 (+0300)
Subject: Align shadow camera to shadow map texels
X-Git-Url: https://git.tdb.fi/?a=commitdiff_plain;h=8bd21199e78616b139cd5f7a18523181ebdfc8d4;p=libs%2Fgl.git

Align shadow camera to shadow map texels

This avoids swimming shadows when the target area moves smoothly.
---

diff --git a/source/effects/shadowmap.cpp b/source/effects/shadowmap.cpp
index 0345ac1f..d945ea6b 100644
--- a/source/effects/shadowmap.cpp
+++ b/source/effects/shadowmap.cpp
@@ -209,7 +209,10 @@ void ShadowMap::setup_frame(Renderer &renderer)
 		if(light.type==DIRECTIONAL)
 		{
 			v.camera.set_object_matrix(*light.light->get_matrix());
-			v.camera.set_position(target);
+			Vector4 pos = v.camera.get_view_matrix()*compose(target, 0.0f);
+			LinAl::Vector<float, 2> texel_size = { radius*2.0f/light.region.width, radius*2.0f/light.region.height };
+			pos = { round(pos.x/texel_size.x)*texel_size.x, round(pos.y/texel_size.y)*texel_size.y, pos.z, 0.0f };
+			v.camera.set_position((v.camera.get_object_matrix()*pos).slice<3>(0));
 			v.camera.set_orthographic(radius*2, radius*2);
 			v.camera.set_depth_clip(-radius, radius);
 		}