omg ça marche

app/src/main/java/chess/view/DDDrender/shader/PieceShader.java

@@ -13,11 +13,20 @@ public class PieceShader extends ShaderProgram {
 
 			uniform mat4 camMatrix;
 			uniform mat4 modelTransform;
+			uniform vec3 lightPosition = vec3(0, 1, 0);
+
+			out vec3 toLightVector;
+			out vec3 surfaceNormal;
 
 			flat out vec3 pass_color;
 
 			void main(void){
-				gl_Position = camMatrix * modelTransform * vec4(position, 1.0);
+				vec4 worldPos = modelTransform * vec4(position, 1.0);
+
+				toLightVector = lightPosition - worldPos.xyz;
+				surfaceNormal = (modelTransform * vec4(normal, 0.0)).xyz;
+
+				gl_Position = camMatrix * worldPos;
 				pass_color = position;
 			}
 				""";
@@ -25,12 +34,24 @@ public class PieceShader extends ShaderProgram {
 	private static String fragmentShader = """
 			#version 330
 
+			in vec3 toLightVector;
+			in vec3 surfaceNormal;
+
 			flat in vec3 pass_color;
 
 			out vec4 out_color;
 
 			void main(void){
-				out_color = vec4(pass_color, 1.0);
+				vec3 unitNormal = normalize(surfaceNormal);
+				vec3 unitLightVector = normalize(toLightVector);
+
+				float diffuse = max(0.5, dot(unitNormal, unitLightVector));
+
+				float brightness = diffuse;
+
+				out_color = vec4(pass_color, 1.0) * brightness;
+				out_color.w = 1.0;
+
 			}
 				""";