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물리 기반 셰이더의 허와 실:물리기반 셰이더를 가르쳐 봤습니다 공개용
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# Wrapped diffuse

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### Wrapped diffuse

1. 1. Wrapped Diffuse 이민웅 Shader Study
2. 2. Wrapped Diffuse • 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
3. 3. Wrapped Diffuse • HarfLambert 공식과 비슷함 – W=1이면, Half Lambert 공식 • Half Lambert와 유사하게 투과되는 느낌을 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 ));
5. 5. Wrapped Diffuse • 팀 포트리스 방식 – Wrapped Function은 Half Lambert를 이용해서, 1D Wrapped Diffuse Texture에서 값을 얻어오 는것 – GPU Gems 16. Real-Time Approximation to Subsurface Scattering • Wrap Lighting 계산 내용을 미리 Texture로 저장하 여 사용함
6. 6. WarpTex Lambert Half Lambert Warping Function Squared Half Lambert (Not used) 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); Light Color Ambient Albedo Ka : ambient Cl : LightColor http://www.sfdm.scad.edu/faculty/mkesson/vsfx419/wip/spring11/eric_kurzmack/toon.html
7. 7. Specular Fresnel Mixed Specular Primary Specularity Rim Fresnel Upward Ambient Rim Final Mix http://www.sfdm.scad.edu/faculty/mkesson/vsfx419/wip/spring11/eric_kurzmack/toon.html Rim Specular
8. 8. Code 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); } 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; Rim Fresnel vector i= normalize(-I); float rimfres=pow((1-(nf.i)),2); vector i= normalize(-I); Upward Ambient Rim float upward = clamp((nf.vector(0,1,0)),0,1); float uprim= upward*rimfres*Kr*(Ka*5); 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); } Final Mix Ci = Oi*(diffusecolor+speccolor+uprim);
9. 9. Q&A
10. 10. 참고자료 • Wrap Shading : http://www.iro.umontreal.ca/~derek/publication8.html • 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/energyconservation-in-games/ • http://www.gamedevforever.com/150 • http://cagetu.egloos.com/5621806
• #### lsh1208

Jun. 27, 2019
• #### taru00

Jul. 27, 2016
• #### JinKyuKim

Jun. 15, 2015

Nov. 6, 2014

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