famous

09-09-2010, 03:09 AM

Hey,

I guess most of you know the relief-mapping algorithm:

f2s main frag relief( v2f IN,

uniform sampler2D rmtex:TEXUNIT0, // rm texture map

uniform sampler2D colortex:TEXUNIT1, // color texture map

uniform float4 lightpos, // light position in view space

uniform float4 ambient, // ambient color

uniform float4 diffuse, // diffuse color

uniform float4 specular, // specular color

uniform float2 planes, // near and far planes info

uniform float tile, // tile factor

uniform float depth) // scale factor for height-field depth

{

f2s OUT;

float4 t,c; float3 p,v,l,s; float2 dp,ds,uv; float d;

// ray intersect in view direction

p = IN.vpos; // pixel position in eye space

v = normalize(p); // view vector in eye space

// view vector in tangent space

s = normalize(float3(dot(v,IN.tangent.xyz),

dot(v,IN.binormal.xyz),dot(IN.normal,-v)));

// size and start position of search in texture space

ds = s.xy*depth/s.z;

dp = IN.texcoord*tile;

...

I'm just wondering about the depth parameter because I don't get why it controls the height of the heightmap details. I.e. if you put in a terrain map, a bigger depth parameter will result in higher mountains etc.

This s.xy*depth/s.z seems like it's the calculation of the parallax vector as described in Welsh's paper (projection of the eye vector onto the surface) and you can scale it with the depth parameter. This means that smaller depth paramter = shorter parallax vector = smaller sampling stepsize. So how does this scale the heightmap at all?

I guess most of you know the relief-mapping algorithm:

f2s main frag relief( v2f IN,

uniform sampler2D rmtex:TEXUNIT0, // rm texture map

uniform sampler2D colortex:TEXUNIT1, // color texture map

uniform float4 lightpos, // light position in view space

uniform float4 ambient, // ambient color

uniform float4 diffuse, // diffuse color

uniform float4 specular, // specular color

uniform float2 planes, // near and far planes info

uniform float tile, // tile factor

uniform float depth) // scale factor for height-field depth

{

f2s OUT;

float4 t,c; float3 p,v,l,s; float2 dp,ds,uv; float d;

// ray intersect in view direction

p = IN.vpos; // pixel position in eye space

v = normalize(p); // view vector in eye space

// view vector in tangent space

s = normalize(float3(dot(v,IN.tangent.xyz),

dot(v,IN.binormal.xyz),dot(IN.normal,-v)));

// size and start position of search in texture space

ds = s.xy*depth/s.z;

dp = IN.texcoord*tile;

...

I'm just wondering about the depth parameter because I don't get why it controls the height of the heightmap details. I.e. if you put in a terrain map, a bigger depth parameter will result in higher mountains etc.

This s.xy*depth/s.z seems like it's the calculation of the parallax vector as described in Welsh's paper (projection of the eye vector onto the surface) and you can scale it with the depth parameter. This means that smaller depth paramter = shorter parallax vector = smaller sampling stepsize. So how does this scale the heightmap at all?