Tag: position

I am trying to recreate positions in Viewspace from only a stored depth value.

In the first pass I store the Normals and the normalized depth in viewspace.
In the second pass I try to build reconstruct the position in viewspace.

I dont know what I am doing wrong, been trying many things, getting out of ideas.
I belive something is going wrong in the reconstruction, but I can’t see what, or if it something else.

The light initially looks fine, but when I start moving around the light seems to be moving around.
When I go futher away, things get less lit. When rotating the light also rotates.

What could I be doing wrong? I want to do the lighting in viewspace, that is what I am trying.

Belove is code for the fragment & vertex shader, first and second pass.

Thank you

First pass:

--Vertex
#version 460

layout( location = 0 ) in vec3 VertexPosition;
layout( location = 1 ) in vec3 VertexNormal;

/* Uniforms */
uniform mat4 ViewMatrix;
uniform mat4 ProjectionMatrix;
uniform mat3 NormalMatrix;
uniform float FarPlane;
uniform float NearPlane;

out vec3 vNormal;
out highp float vDepth;

void main() {
  mat4 vMVP = ProjectionMatrix * ViewMatrix;
  gl_Position = vMVP * vec4( VertexPosition, 1.0 ); // Screenspace

  vNormal = normalize(NormalMatrix  * normalize(VertexNormal));
  vec3 vPos = (ViewMatrix * vec4( VertexPosition, 1.0 )).xyz;

  // Save normalized depth (0, 1)
  vDepth = -(vPos.z - NearPlane) / ( FarPlane - NearPlane);
}

--Fragment
#version 460

in vec3 vNormal;
in highp float vDepth;

layout (location = 0) out highp vec4 NormalDepth;

void main() {
  NormalDepth = vec4(normalize(vNormal), vDepth);
}

Second pass (off rendering to screen):

--Vertex
#version 460

layout( location = 0 ) in vec3 VertexPosition;

out vec2 vTexCoord;
out vec2 vDeviceCoords;

void main() {
  vDeviceCoords = 2.0 * ( VertexPosition.xy - 0.5 );// (-1, 1)
  vTexCoord = VertexPosition.xy;//  (0, 1) // Just 2 triangles for the screen

  gl_Position = vec4(vDeviceCoords, 1.0, 1.0 ); // (-1, 1)
}

--Fragment
#version 460

/* Uniforms */
uniform float NearPlane;
uniform float FarPlane;
uniform mat4 ViewMatrix;

/*  From prev shader stage */
in vec2 vTexCoord;
in vec2 vDeviceCoords;

/* Out */
layout( location = 0 ) out vec4 FragColor;

/* In */
layout( binding = 0 ) uniform highp sampler2D NormalDepthTex;

vec3 diffuseValue( vec3 color, vec3 normal, vec3 position)
{
  // Light position. Here now for testing purposes
  // Stationary point light, transformed to viewspace
  vec3 vLightPos = (ViewMatrix * vec4( -10.0, 0.0, 2.0, 1.0 )).xyz;

  normal = normalize(normal);
  const vec3 lightDir = normalize(position - vLightPos);
  const float diffuseCos = max( dot( normal, -lightDir ), 0.0 );

  return diffuseCos ;
}

void main() {
  const vec4 normalDepth = texture2D( NormalDepthTex, vTexCoord );

  // Normalize depth to (0, FarPlane)
  const float depth = normalDepth.w * (FarPlane - NearPlane);

  // Unproject
  vec3 position;
  position = vec3(vDeviceCoords.x, vDeviceCoords.y, NearPlane);
  position.xy *= depth / near; 
  position.z = depth;

  // View space
  vec3 diffuseValue = diffuseValue(normalDepth.xyz, position);

  FragColor = vec4( diffuseValue.x, diffuseValue.y, diffuseValue.z, 1.0 );
}

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