I'm doing per-pixel lighting(phong shading) on my terrain. I'm using a heightmap to generate the terrain height and then calculating the normal for each vertex. The normals are interpolated in the fragment shader and also normalized.
I am getting some weird dark lines near the edges of triangles where there shouldn't be. https://i.stack.imgur.com/OP9gF.jpg
I checked if the normals were correct using a geometry shader to draw the normals on the terrain and they seem to be correct. https://i.stack.imgur.com/xLNNR.jpg
There is no point using a normal map for the terrain it will just give pretty much the same normals. The problem lies with the way the normals are interpolated across a triangle.
I am out of idea's how to solve this. I couldn't find any working solution online.
Terrain Vertex Shader:
#version 330 core
layout (location = 0) in vec3 position;
layout (location = 1) in vec3 normal;
layout (location = 2) in vec2 textureCoords;
out vec2 pass_textureCoords;
out vec3 surfaceNormal;
out vec3 toLightVector;
out float visibility;
uniform mat4 transformationMatrix;
uniform mat4 viewMatrix;
uniform mat4 projectionMatrix;
uniform vec3 lightPosition;
const float density = 0.0035;
const float gradient = 5.0;
void main()
{
vec4 worldPosition = transformationMatrix * vec4(position, 1.0f);
vec4 positionRelativeToCam = viewMatrix * worldPosition;
gl_Position = projectionMatrix * positionRelativeToCam;
pass_textureCoords = textureCoords;
surfaceNormal = (transformationMatrix * vec4(normal, 0.0f)).xyz;
toLightVector = lightPosition - worldPosition.xyz;
float distance = length(positionRelativeToCam.xyz);
visibility = exp(-pow((distance * density), gradient));
visibility = clamp(visibility, 0.0, 1.0);
}
Terrain Fragment Shader:
#version 330 core
in vec2 pass_textureCoords;
in vec3 surfaceNormal;
in vec3 toLightVector;
in float visibility;
out vec4 colour;
uniform vec3 lightColour;
uniform vec3 fogColour;
uniform sampler2DArray blendMap;
uniform sampler2DArray diffuseMap;
void main()
{
vec4 blendMapColour = texture(blendMap, vec3(pass_textureCoords, 0));
float backTextureAmount = 1 - (blendMapColour.r + blendMapColour.g + blendMapColour.b);
vec2 tiledCoords = pass_textureCoords * 255.0;
vec4 backgroundTextureColour = texture(diffuseMap, vec3(tiledCoords, 0)) * backTextureAmount;
vec4 rTextureColour = texture(diffuseMap, vec3(tiledCoords, 1)) * blendMapColour.r;
vec4 gTextureColour = texture(diffuseMap, vec3(tiledCoords, 2)) * blendMapColour.g;
vec4 bTextureColour = texture(diffuseMap, vec3(tiledCoords, 3)) * blendMapColour.b;
vec4 diffuseColour = backgroundTextureColour + rTextureColour + gTextureColour + bTextureColour;
vec3 unitSurfaceNormal = normalize(surfaceNormal);
vec3 unitToLightVector = normalize(toLightVector);
float brightness = dot(unitSurfaceNormal, unitToLightVector);
float ambient = 0.2;
brightness = max(brightness, ambient);
vec3 diffuse = brightness * lightColour;
colour = vec4(diffuse, 1.0) * diffuseColour;
colour = mix(vec4(fogColour, 1.0), colour, visibility);
}
