Wrapped Diffuse

이민웅 Shader Study

Wrapped Diffuse

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팀 포트리스 2에서 사용 subsurface scattering, area light source, 더 부드러운 reflectance 를 표현하기 위해 서 Hemisphere(반구)를 감싸는 셰이딩 모 델

Lambert Wrapped Diffuse

Wrapped Diffuse

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HarfLambert 공식과 비슷함

– W=1이면, Half Lambert 공식

Half Lambert와 유사하게 투과되는 느낌 을 표현하는데 많이 사용

– 피부, 나뭇잎, 파티클 라이팅에 주로 사용

기본 Lambert Diffuse 공식 float diffuse = max(0, dot(normal, lightdirection)); 기본 HalfLambert Diffuse 공식 float halflambert_term = dot(normal, lightdirection) * 0.5f + 0.5f

Wrapped Diffuse 공식 float diffuse = saturate((dot(normal, lightdirection) + OFFSET) / (1.0+OFFSET ));

Wrapped Diffuse

Wrapped SH 자세한 내용 http://blog.selfshadow.com/2011/12/31/righting-wrap-part-1/ http://blog.selfshadow.com/2012/01/07/righting-wrap-part-2/

Wrap Shading

www.iro.umontreal.ca/~derek/files/jgt_

wrap

.pdf

Wrapped Diffuse

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팀 포트리스 방식

– Wrapped Function은 Half Lambert를 이용해 서, 1D Wrapped Diffuse Texture에서 값을 얻 어오는 것 – GPU Gems 16. Real-Time Approximation to Subsurface Scattering • Wrap Lighting 계산 내용을 미리 Texture로 저장하 여 사용함

Lambert Half Lambert Squared Half Lambert (Not used) Warping Function WarpTex

illuminance( P, n, PI) { Ln = normalize(L); halflambert += .5*(Ln.nf)+.5; float chl = clamp(halflambert,0.01,1); accumulateMapColor = texture(warp,chl,0)*2; hlsw_clrlght += Cl*accumulateMapColor; } diffusecolor = albedocolor * (Ka + hlsw_clrlght); Ka : ambient Cl : LightColor

Light Color Ambient Albedo

http://www.sfdm.scad.edu/faculty/mkesson/vsfx419/wip/spring11/eric_kurzmack/toon.html

Specular Fresnel Primary Specularity Rim Fresnel Rim Specular Mixed Specular Upward Ambient Rim Final Mix

http://www.sfdm.scad.edu/faculty/mkesson/vsfx419/wip/spring11/eric_kurzmack/toon.html

Specular Fresnel

vector i= normalize(-I); float fres=spline((nf.i),1,1,1,.95,.6,.6);

Primary Specularity

} illuminance( P, n, PI/2) { Ln = normalize(L); vector R = reflect(-Ln,nf); ridot += clamp(max(0,(R.i)),.01,.99); phngspec += (1-fres)*pow(ridot,specE);

Rim Fresnel

vector i= normalize(-I); float rimfres=pow((1-(nf.i)),2); vector i= normalize(-I);

Rim Specular

} illuminance( P, n, PI/2) { Ln = normalize(L); vector R2 = reflect(Ln,nf); ridot2 += clamp(max(0,(R2.i)),.01,.99); phngrim += rimfres*pow(ridot2,Krim); Code

Mixed Specular

illuminance( P, n, PI/2) { Ln = normalize(L); vector R = reflect(-Ln,nf); vector R2 = reflect(Ln,nf); ridot += clamp(max(0,(R.i)),.01,.99); ridot2 += clamp(max(0,(R2.i)),.01,.99); phngspec += (1-fres)*pow(ridot,specE); phngrim += rimfres*pow(ridot2,Krim); phngmix += Cl*Ks*(max(phngrim,phngspec)*2); } speccolor = phngmix;

Upward Ambient Rim

float upward = clamp((nf.vector(0,1,0)),0,1); float uprim= upward*rimfres*Kr*(Ka*5);

Final Mix

Ci = Oi*(diffusecolor+speccolor+uprim);

Q&A

참고자료 • • • • • • • l Wrap Shading : http://www.iro.umontreal.ca/~derek/publication8.htm

Energy-Conserving Wrapped Diffuse Wrapped Diffuse와 팀포트리스 셰이딩 : http://cagetu.egloos.com/5621806 팀포트리스 셰이딩 따라해보기 : http://cagetu.egloos.com/4212681 Energy Conservation in Games : http://www.rorydriscoll.com/2009/01/25/energy conservation-in-games/ http://www.gamedevforever.com/150 http://cagetu.egloos.com/5621806