New user here, so HI!
As the title suggests, I could use some assistance in implementing basic parallax occlusion mapping.
The image below shows the issue I am having:
[attachment=21988:parallaxerror.jpg]
The wall on the right is where the artefact is (I've increased the parallax scale to make the artefact more visible).
The mesh used is a simple plane. The wall on the left is rotation 90 degrees on the X axis, and is totally fine, but the wall on the right is rotated -90 degrees. I have tried rotating the wall +90 on X and then 180 on Y to orientate it correctly, which produces the same artefact.
I have followed the tutorials I found very closely, but as the image shows, the uv offsetting on the right wall is incorrect, and I can't figure out why.
My method is to transform the texture based normal out of tangent space, into world space (which you will see in the shader source below), and not modify the view vector in any way.
I could really use some help with this, as I really don't understand what is causing this error.
Shader source:
// -----------------------------------------------------------------------------------------------------------
// parallax vertex shader
#version 330
//per vertex inputs stored on GPU memory
in vec3 in_Position;
in vec3 in_Normal;
in vec2 in_TexCoord;
in vec4 tangent;
//per mesh data sent at rendering time
uniform mat4 model; //object to world space transformations
uniform mat4 view; //world to eye space transformations
uniform mat4 projection; //eye space to screen space
uniform mat3 normalMat; //for transforming normals in
uniform vec4 lightPosition; //light position in world space
uniform vec3 eyePosition; //eye position in world space
//outputs to fragment shader
out VertexData
{
vec3 position; //vertex position in eye space
vec3 ex_L; //light vector
vec3 ex_V; //view direction
vec3 ex_N;
mat3 tbn; //TBN matrix for tangent/world transformations
vec2 ex_TexCoord;
float dist;
} vertex;
void main(void)
{
//view space position for lighting calculations
vertex.position = vec3(model * vec4(in_Position,1.0));
//calculate view vector and light vector in world space
vertex.ex_V = normalize(eyePosition-vertex.position);
vertex.ex_L = lightPosition.xyz - vertex.position;
vertex.ex_TexCoord = in_TexCoord;
//now calculate tbn matrix, and transform the view & light vectors into tangent space
vertex.ex_N = (model * vec4( in_Normal,0.0)).xyz;
vec3 tan = (model * vec4( tangent.xyz,0.0)).xyz;
vec3 BiTan = cross(vertex.ex_N, tangent.xyz)*tangent.w;
vertex.dist = length(vertex.ex_L);
vertex.tbn = mat3(tan,BiTan,vertex.ex_N);
gl_Position = projection * view * vec4(vertex.position,1.0);
}
//End vertex shader
// ------------------------------------------------------------------------------------------------------------------------
// parallax fragment shader
#version 330
// Some drivers require the following
precision highp float;
struct lightStruct
{
vec4 ambient;
vec4 diffuse;
vec4 specular;
vec4 position;
float radius;
};
struct materialStruct
{
vec4 ambient;
vec4 diffuse;
vec4 specular;
vec4 emissive;
float shininess;
};
//uniforms sent at render time
uniform lightStruct light;
uniform materialStruct material;
uniform vec2 scaleBias;
//texture information
uniform sampler2D colourMap;
uniform sampler2D normalMap;
uniform sampler2D specularMap;
uniform sampler2D heightMap;
uniform sampler2D glossMap;
//inputs from vertex shader stage
in VertexData
{
vec3 position; //vertex position in eye space
vec3 ex_L; //light vector
vec3 ex_V; //view direction
vec3 ex_N;
mat3 tbn; //TBN matrix for tangent/world transformations
vec2 ex_TexCoord;
float dist;
} vertex;
//final fragment colour
layout(location = 0) out vec4 out_Color;
void main(void) {
//calculate halfway vector for blinn phong
vec3 Half = normalize(vertex.ex_V + normalize(vertex.ex_L));
vec2 texCoord;
vec3 diffuseTexel ;
vec3 specularTexel;
float gloss;
vec3 normal;
//sample textures
//first get our parallax values
float height = texture(heightMap,vertex.ex_TexCoord.st).r;
height = height * scaleBias.r - scaleBias.g;
texCoord = vertex.ex_TexCoord.st + (normalize(vertex.ex_V).xy * height);
diffuseTexel = texture(colourMap,texCoord.st).rgb;
specularTexel = texture(specularMap,texCoord.st).rgb;
//normal maps are encoded with values between 0.0 and 0.5 being negative, so need to remove the encoding.
normal = vertex.tbn * normalize(texture(normalMap,texCoord.st).rgb * 2.0 - 1.0);
gloss = texture(glossMap,texCoord.st).r;
float lambert = dot(normal, normalize(vertex.ex_L));
vec3 litColour = vec3(0.0,0.0,0.0);
//if light is worth calculating
if (lambert > 0.0)
{
vec3 R = normalize(-reflect(vertex.ex_L,normal));
float spectral = pow(max(dot(R,vertex.ex_V),0.0),material.shininess );
litColour += light.diffuse.xyz * material.diffuse.xyz * lambert;
litColour += light.specular.xyz * material.specular.xyz * spectral * gloss;
float attenuation = 1.0 + (0.01 * vertex.dist*vertex.dist) + (0.01 * vertex.dist);
attenuation = 1.0/attenuation;
litColour *= attenuation;
}
out_Color = vec4( litColour *diffuseTexel*specularTexel ,1.0);
}
