Normal Mapping Precision on iOS
I was using ZBrush alot lately, and want to get normal mapping working on ios.
I have implemented a normal mapping glsl shader that works, but I see subtle "banding" on the lit parts of the model.
The shader works great when I run it on the mac with no banding  it's only on ios that I see the effect.
I am thinking it might be a problem with the precision of the texture sampler on ios.
Is this a known issue  should I look into encoding the normals in a more effecient fashion...
I am using the stock tangent space normal map coming out of zbrush, which I think encodes nx,ny,nz in r,g,b and ignores a.
Thanks for any advice...
I have implemented a normal mapping glsl shader that works, but I see subtle "banding" on the lit parts of the model.
The shader works great when I run it on the mac with no banding  it's only on ios that I see the effect.
I am thinking it might be a problem with the precision of the texture sampler on ios.
Is this a known issue  should I look into encoding the normals in a more effecient fashion...
I am using the stock tangent space normal map coming out of zbrush, which I think encodes nx,ny,nz in r,g,b and ignores a.
Thanks for any advice...
GLSL ES has the concept of "precision" within the shader. This allows you to potentially sacrifice precision in your results to run faster.
Long story short, the default precision for the fragment shader is "mediump"; did you change it?
Long story short, the default precision for the fragment shader is "mediump"; did you change it?
Yes  I have tried using highp for everything...
still same banding is present.
It is like the actual sampler is returning lower precision normals.
on mac:
on ios:
Thanks again for any advice....
still same banding is present.
It is like the actual sampler is returning lower precision normals.
on mac:
on ios:
Thanks again for any advice....
Samplers also have associated precision, did you set the precision on the sampler? Additionally, the default precision for samplers is "lowp".
Maybe you should post your shader code.
Maybe you should post your shader code.
What texture format are you using?
I tried it with the samplers explicitly set to highp  same issue...
I tried limiting the fragcolor to just a solid color modulated by nDotL...
and I still see the banding...it seems to be an artifact of how I am calculating nDotL.
Here are the shaders (sorry I haven't taken time to clean them up)
Vertex Shader
Fragment Shader
Thanks again for any advice....
I tried limiting the fragcolor to just a solid color modulated by nDotL...
and I still see the banding...it seems to be an artifact of how I am calculating nDotL.
Here are the shaders (sorry I haven't taken time to clean them up)
Vertex Shader
Code:
attribute vec4 position;
attribute vec3 normal;
attribute vec3 binormal;
attribute vec3 tangent;
attribute vec2 texcoord0;
attribute vec4 color;
varying vec4 colorVarying;
varying vec2 texOut0;
varying vec3 v_viewDirection;
varying vec3 v_lightDirection;
varying vec3 v_normal;
uniform float translate;
uniform mat4 u_mvp_matrix;
uniform mat4 Projection;
uniform mat4 Modelview;
uniform mat4 ModelviewInverse;
uniform mat3 NormalMatrix;
uniform vec3 LightPosition;
uniform vec3 EyePosition;
void main()
{
vec3 vRed = vec3(1,0,0);
gl_Position = Projection * Modelview * position;
texOut0 = texcoord0;
vec3 worldPosition = (Modelview * position).xyz;
vec3 normalWorld = normalize((NormalMatrix * normal).xyz);
vec3 eyePositionWorld = ( ModelviewInverse * vec4(EyePosition,1.0)).xyz;
vec3 viewDirectionWorld = eyePositionWorld  position.xyz;
vec3 lightPositionWorld = ( ModelviewInverse * vec4(LightPosition,1.0)).xyz;
vec3 lightDirectionWorld = lightPositionWorld  position.xyz;
mat3 tangentMat = mat3(tangent,binormal,normal.xyz);
v_viewDirection = viewDirectionWorld * tangentMat;
v_lightDirection = lightDirectionWorld * tangentMat;
}
Fragment Shader
Code:
precision highp float;
varying lowp vec4 colorVarying;
varying lowp vec2 texOut0;
varying mediump vec3 v_normal;
uniform sampler2D textureMap;
uniform sampler2D normalMap;
varying mediump vec3 v_viewDirection;
varying mediump vec3 v_lightDirection;
void main()
{
highp vec3 baseColor = texture2D( textureMap, texOut0.st).xyz;
//lowp vec4 baseColor = vec4(1,1,1,1);
highp vec3 nl = texture2D( normalMap, texOut0.st).xyz;
highp vec3 normal = normalize(nl.yxz * 2.0 1.0);
highp vec3 lightDirection = normalize(v_lightDirection);
highp vec3 viewDirection = normalize(v_viewDirection);
highp float nDotL = dot(normal, lightDirection);
highp vec3 reflection = (2.0 * normal * nDotL)  lightDirection;
highp float rDotV = max( 0.0,dot(reflection, viewDirection));
// mediump vec4 ambient = vec4(0.1,0.1,0.1,1.0) * baseColor;
// mediump vec4 diffuse = vec4(0.8,0.8,0.8,1.0) * nDotL * baseColor;
// mediump vec4 specular = vec4(1,1,1,1) * pow(rDotV, 100.0);
//gl_FragColor= ambient + diffuse + specular;
highp vec3 ambient = vec3(0.1,0.1,0.1) * baseColor;
highp vec3 diffuse = vec3(1.0,1.0,1.0) * nDotL * baseColor;
highp vec3 specular = vec3(1,1,1) * pow(rDotV, 100.0);
gl_FragColor= vec4(ambient + diffuse + specular,1);
//gl_FragColor= diffuse;
//gl_FragColor = vec4(nl,1);
}
Thanks again for any advice....
arekkusu  You are Open GL master!
I was using a Texture loader that was incorrectly picking RGB565!
Once I used rgba8888 all was perfect!
Thank you  I have been struggling with this all day :)
And thank you too OSC !
:)
I was using a Texture loader that was incorrectly picking RGB565!
Once I used rgba8888 all was perfect!
Thank you  I have been struggling with this all day :)
And thank you too OSC !
:)
Possibly Related Threads...
Thread:  Author  Replies:  Views:  Last Post  
Getting the Normal for a polygon.  Jaden  3  8,109 
May 1, 2009 01:47 PM Last Post: Nosredna 

Poor precision in depth texture  TomorrowPlusX  59  60,423 
Jul 3, 2007 12:23 AM Last Post: Ciaran 

Vector (Normal) Map blending operations?  kelvin  10  10,960 
Mar 16, 2007 04:31 PM Last Post: OneSadCookie 

drawing or displaying vertex normal  shru_ani  3  5,638 
Oct 29, 2006 06:04 AM Last Post: shru_ani 

Gouraud vs Normal maps for dinamic terrains  sohta  6  7,166 
Oct 11, 2006 12:55 AM Last Post: sohta 