From b71861114926dd161a76202559e03ae7b12ac34e Mon Sep 17 00:00:00 2001
From: bloeys <bloeys@outlook.com>
Date: Sun, 14 Apr 2024 03:45:48 +0400
Subject: [PATCH] Improving shadows

---
 main.go                 | 36 ++++++++++++++++++++++++++----------
 res/shaders/simple.glsl | 10 +++++++---
 2 files changed, 33 insertions(+), 13 deletions(-)

diff --git a/main.go b/main.go
index aba6b96..e36177e 100755
--- a/main.go
+++ b/main.go
@@ -51,7 +51,7 @@ type DirLight struct {
 }
 
 var (
-	dSize float32 = 50
+	dSize float32 = 30
 	dNear float32 = 1
 	dFar  float32 = 50
 	dPos          = gglm.NewVec3(0, 10, 0)
@@ -163,7 +163,7 @@ var (
 
 	// Lights
 	dirLight = DirLight{
-		Dir:           *gglm.NewVec3(0.57735, -0.57735, 0.57735).Normalize(),
+		Dir:           *gglm.NewVec3(0, -0.5, -0.8).Normalize(),
 		DiffuseColor:  *gglm.NewVec3(1, 1, 1),
 		SpecularColor: *gglm.NewVec3(1, 1, 1),
 	}
@@ -848,10 +848,19 @@ func (g *Game) Render() {
 
 	depthMapMat.SetUnifMat4("projViewMat", &dirLightProjViewMat)
 
+	//
 	// Render depth map for shadows
+	//
 	depthMapFbo.BindWithViewport()
 	depthMapFbo.Clear()
+
+	// Culling front faces helps 'peter panning' when
+	// drawing shadow maps, but works only for solids with a back face (i.e. quads won't cast shadows).
+	// Check more here: https://learnopengl.com/Advanced-Lighting/Shadows/Shadow-Mapping
+	gl.CullFace(gl.FRONT)
 	g.RenderScene(depthMapMat)
+	gl.CullFace(gl.BACK)
+
 	depthMapFbo.UnBindWithViewport(uint32(g.WinWidth), uint32(g.WinHeight))
 
 	if renderToDepthMapFbo {
@@ -932,14 +941,21 @@ func (g *Game) RenderScene(overrideMat *materials.Material) {
 	window.Rend.DrawMesh(cubeMesh, gglm.NewTrMatId().Translate(gglm.NewVec3(0, -3, 0)).Scale(gglm.NewVec3(20, 1, 20)), cubeMat)
 
 	// Cubes
-	rowSize := 1
-	for y := 0; y < rowSize; y++ {
-		for x := 0; x < rowSize; x++ {
-			tempModelMatrix.Translate(gglm.NewVec3(-6, 0, 0))
-			window.Rend.DrawMesh(cubeMesh, tempModelMatrix, cubeMat)
-		}
-		tempModelMatrix.Translate(gglm.NewVec3(float32(rowSize), -1, 0))
-	}
+	tempModelMatrix.Translate(gglm.NewVec3(-6, 0, 0))
+	window.Rend.DrawMesh(cubeMesh, tempModelMatrix, cubeMat)
+
+	tempModelMatrix.Translate(gglm.NewVec3(0, -1, -4))
+	window.Rend.DrawMesh(cubeMesh, tempModelMatrix, cubeMat)
+
+	// Cubes generator
+	// rowSize := 1
+	// for y := 0; y < rowSize; y++ {
+	// 	for x := 0; x < rowSize; x++ {
+	// 		tempModelMatrix.Translate(gglm.NewVec3(-6, 0, 0))
+	// 		window.Rend.DrawMesh(cubeMesh, tempModelMatrix, cubeMat)
+	// 	}
+	// 	tempModelMatrix.Translate(gglm.NewVec3(float32(rowSize), -1, 0))
+	// }
 }
 
 func (g *Game) DrawSkybox() {
diff --git a/res/shaders/simple.glsl b/res/shaders/simple.glsl
index b98ad79..085adf5 100755
--- a/res/shaders/simple.glsl
+++ b/res/shaders/simple.glsl
@@ -99,7 +99,7 @@ vec4 emissionTexColor;
 vec3 normalizedVertNorm;
 vec3 viewDir;
 
-float CalcShadow(sampler2D shadowMap)
+float CalcShadow(sampler2D shadowMap, vec3 lightDir)
 {
     // Move from clip space to NDC
     vec3 projCoords = fragPosDirLight.xyz / fragPosDirLight.w;
@@ -113,9 +113,13 @@ float CalcShadow(sampler2D shadowMap)
     // Closest depth is the closest depth value from the light's perspective
     float closestDepth = texture(shadowMap, projCoords.xy).r;
 
+    // Bias in the range [0.005, 0.05] depending on the angle, where a higher
+    // angle gives a higher bias, as shadow acne gets worse with angle
+    float bias = max(0.05 * (1.0 - dot(normalizedVertNorm, lightDir)), 0.005);
+
     // If our depth is larger than the lights closest depth,
     // then there is something closer to the light than us, and so we are in shadow
-    float shadow = currentDepth > closestDepth  ? 1.0 : 0.0;
+    float shadow = currentDepth - bias > closestDepth  ? 1.0 : 0.0;
 
     return shadow;
 }
@@ -134,7 +138,7 @@ vec3 CalcDirLight()
     vec3 finalSpecular = specularAmount * dirLight.specularColor * specularTexColor.rgb;
 
     // Shadow
-    float shadow = CalcShadow(dirLight.shadowMap);
+    float shadow = CalcShadow(dirLight.shadowMap, lightDir);
 
     return (finalDiffuse + finalSpecular) * (1.0 - shadow);
 }