diff --git a/src/common/rendering/vulkan/accelstructs/vk_lightmap.cpp b/src/common/rendering/vulkan/accelstructs/vk_lightmap.cpp
index de797519d..4e1e2887e 100644
--- a/src/common/rendering/vulkan/accelstructs/vk_lightmap.cpp
+++ b/src/common/rendering/vulkan/accelstructs/vk_lightmap.cpp
@@ -140,6 +140,12 @@ void VkLightmap::RenderBakeImage()
 	cmdbuffer->bindDescriptorSet(VK_PIPELINE_BIND_POINT_GRAPHICS, raytrace.pipelineLayout.get(), 0, raytrace.descriptorSet0.get());
 	cmdbuffer->bindDescriptorSet(VK_PIPELINE_BIND_POINT_GRAPHICS, raytrace.pipelineLayout.get(), 1, raytrace.descriptorSet1.get());
 
+	VkViewport viewport = {};
+	viewport.maxDepth = 1;
+	viewport.width = (float)bakeImageSize;
+	viewport.height = (float)bakeImageSize;
+	fb->GetCommands()->GetTransferCommands()->setViewport(0, 1, &viewport);
+
 	for (int i = 0, count = selectedSurfaces.Size(); i < count; i++)
 	{
 		auto& selectedSurface = selectedSurfaces[i];
@@ -151,14 +157,6 @@ void VkLightmap::RenderBakeImage()
 			continue;
 		}
 
-		VkViewport viewport = {};
-		viewport.maxDepth = 1;
-		viewport.x = (float)selectedSurface.X - 1;
-		viewport.y = (float)selectedSurface.Y - 1;
-		viewport.width = (float)(targetSurface->texWidth + 2);
-		viewport.height = (float)(targetSurface->texHeight + 2);
-		fb->GetCommands()->GetTransferCommands()->setViewport(0, 1, &viewport);
-
 		bool buffersFull = false;
 
 		// Paint all surfaces part of the smoothing group into the surface
@@ -198,19 +196,20 @@ void VkLightmap::RenderBakeImage()
 			LightmapPushConstants pc;
 			pc.LightStart = firstLight;
 			pc.LightEnd = firstLight + lightCount;
-			pc.TileX = selectedSurface.X;
-			pc.TileY = selectedSurface.Y;
+			pc.TileX = (float)selectedSurface.X;
+			pc.TileY = (float)selectedSurface.Y;
 			pc.SurfaceIndex = mesh->GetSurfaceIndex(targetSurface);
+			pc.TextureSize = (float)bakeImageSize;
 			pc.LightmapOrigin = targetSurface->worldOrigin - targetSurface->worldStepX - targetSurface->worldStepY;
 			pc.LightmapStepX = targetSurface->worldStepX * viewport.width;
 			pc.LightmapStepY = targetSurface->worldStepY * viewport.height;
-			pc.TileWidth = targetSurface->texWidth;
-			pc.TileHeight = targetSurface->texHeight;
+			pc.TileWidth = (float)targetSurface->texWidth;
+			pc.TileHeight = (float)targetSurface->texHeight;
 			pc.WorldToLocal = targetSurface->translateWorldToLocal;
 			pc.ProjLocalToU = targetSurface->projLocalToU;
 			pc.ProjLocalToV = targetSurface->projLocalToV;
-			fb->GetCommands()->GetTransferCommands()->pushConstants(raytrace.pipelineLayout.get(), VK_SHADER_STAGE_VERTEX_BIT | VK_SHADER_STAGE_FRAGMENT_BIT, 0, sizeof(LightmapPushConstants), &pc);
 
+			fb->GetCommands()->GetTransferCommands()->pushConstants(raytrace.pipelineLayout.get(), VK_SHADER_STAGE_VERTEX_BIT | VK_SHADER_STAGE_FRAGMENT_BIT, 0, sizeof(LightmapPushConstants), &pc);
 			fb->GetCommands()->GetTransferCommands()->drawIndexed(surface->numElements, 1, surface->startElementIndex, 0, 0);
 		}
 
diff --git a/src/common/rendering/vulkan/accelstructs/vk_lightmap.h b/src/common/rendering/vulkan/accelstructs/vk_lightmap.h
index 203e1bd2c..d0ebbcf64 100644
--- a/src/common/rendering/vulkan/accelstructs/vk_lightmap.h
+++ b/src/common/rendering/vulkan/accelstructs/vk_lightmap.h
@@ -24,7 +24,7 @@ struct LightmapPushConstants
 	int32_t SurfaceIndex;
 	int32_t PushPadding1;
 	FVector3 LightmapOrigin;
-	float PushPadding2;
+	float TextureSize;
 	FVector3 LightmapStepX;
 	float PushPadding3;
 	FVector3 LightmapStepY;
@@ -35,10 +35,10 @@ struct LightmapPushConstants
 	float PushPadding6;
 	FVector3 ProjLocalToV;
 	float PushPadding7;
-	int32_t TileX;
-	int32_t TileY;
-	int32_t TileWidth;
-	int32_t TileHeight;
+	float TileX;
+	float TileY;
+	float TileWidth;
+	float TileHeight;
 };
 
 struct LightmapBakeImage
diff --git a/wadsrc/static/shaders/lightmap/frag_raytrace.glsl b/wadsrc/static/shaders/lightmap/frag_raytrace.glsl
index ae061f22a..eb743505a 100644
--- a/wadsrc/static/shaders/lightmap/frag_raytrace.glsl
+++ b/wadsrc/static/shaders/lightmap/frag_raytrace.glsl
@@ -75,7 +75,7 @@ layout(push_constant) uniform PushConstants
 	int SurfaceIndex;
 	int PushPadding1;
 	vec3 LightmapOrigin;
-	float PushPadding2;
+	float TextureSize;
 	vec3 LightmapStepX;
 	float PushPadding3;
 	vec3 LightmapStepY;
@@ -86,10 +86,10 @@ layout(push_constant) uniform PushConstants
 	float PushPadding6;
 	vec3 ProjLocalToV;
 	float PushPadding7;
-	int TileX;
-	int TileY;
-	int TileWidth;
-	int TileHeight;
+	float TileX;
+	float TileY;
+	float TileWidth;
+	float TileHeight;
 };
 
 layout(location = 0) centroid in vec3 worldpos;
diff --git a/wadsrc/static/shaders/lightmap/vert_raytrace.glsl b/wadsrc/static/shaders/lightmap/vert_raytrace.glsl
index 2388b5cdb..e59b84029 100644
--- a/wadsrc/static/shaders/lightmap/vert_raytrace.glsl
+++ b/wadsrc/static/shaders/lightmap/vert_raytrace.glsl
@@ -6,7 +6,7 @@ layout(push_constant) uniform PushConstants
 	int SurfaceIndex;
 	int PushPadding1;
 	vec3 LightmapOrigin;
-	float PushPadding2;
+	float TextureSize;
 	vec3 LightmapStepX;
 	float PushPadding3;
 	vec3 LightmapStepY;
@@ -17,10 +17,10 @@ layout(push_constant) uniform PushConstants
 	float PushPadding6;
 	vec3 ProjLocalToV;
 	float PushPadding7;
-	int TileX;
-	int TileY;
-	int TileWidth;
-	int TileHeight;
+	float TileX;
+	float TileY;
+	float TileWidth;
+	float TileHeight;
 };
 
 layout(location = 0) in vec3 aPosition;
@@ -28,11 +28,19 @@ layout(location = 0) out vec3 worldpos;
 
 void main()
 {
-	vec3 localPos = aPosition - WorldToLocal;
-	float u = (1.0f + dot(localPos, ProjLocalToU)) / float(TileWidth + 2);
-	float v = (1.0f + dot(localPos, ProjLocalToV)) / float(TileHeight + 2);
+	worldpos = aPosition;
 
-	worldpos = LightmapOrigin + LightmapStepX * u + LightmapStepY * v;
-	gl_Position = vec4(vec2(u, v) * 2.0 - 1.0, 0.0, 1.0);
+	// Project to position relative to tile
+	vec3 localPos = aPosition - WorldToLocal;
+	float x = 1.0 + dot(localPos, ProjLocalToU);
+	float y = 1.0 + dot(localPos, ProjLocalToV);
+
+	// Find the position in the output texture
+	gl_Position = vec4(vec2(TileX + x, TileY + y) / TextureSize * 2.0 - 1.0, 0.0, 1.0);
+
+	// Clip all surfaces to the edge of the tile (effectly we are applying a viewport/scissor to the tile)
+	gl_ClipDistance[0] = x;
+	gl_ClipDistance[1] = y;
+	gl_ClipDistance[2] = TileWidth + 2.0 - x;
+	gl_ClipDistance[3] = TileHeight + 2.0 - y;
 }
- 
\ No newline at end of file