That normal map is in tangent-space, but you are treating it as object-space. You need a bitangent and/or tangent vector per-vertex in ...
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ImplementingNormalMappingusingOpenGL/GLSL
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Asked
7years,2monthsago
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4years,4monthsago
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1
I'mlearningGLSLandtryingtoimplementsomelightingandmappingtricks.I'mworkingwithShaderDesignertool.AftercodingnormalmappingIrecognizedthatmymodelilluminationlooksnotreal.Hereismycodeandsomepictures.Ifitpossibletellmewhatismyproblem.
VertexShader
#defineMAX_LIGHTS1
structLightProps
{
vec3direction[MAX_LIGHTS];
};
attributevec3tangent;
attributevec3bitangent;
varyingLightPropslights;
voidmain()
{
vec3N=normalize(gl_NormalMatrix*gl_Normal);
vec3T=normalize(gl_NormalMatrix*tangent);
vec3B=normalize(gl_NormalMatrix*bitangent);
mat3TBNMatrix=mat3(T,B,N);
vec4vertex=gl_ModelViewMatrix*gl_Vertex;
for(inti=0;i0?lightPos-vertex:lightPos);
lights.direction[i]*=TBNMatrix;
}
gl_TexCoord[0]=gl_MultiTexCoord0;
gl_Position=gl_ModelViewProjectionMatrix*gl_Vertex;
}
FragmentShader
#defineMAX_LIGHTS1
structLightProps
{
vec3direction[MAX_LIGHTS];
};
uniformsampler2DtextureUnit;
uniformsampler2DnormalTextureUnit;
uniformvec4TexColor;
varyingLightPropslights;
voidmain()
{
vec3N=normalize(texture2D(normalTextureUnit,gl_TexCoord[0].st).rgb*2.0-1.0);
vec4color=vec4(0,0,0,0);
for(inti=0;i0)
{
floatatt=1.0;
if(gl_LightSource[i].position.w>0)
{
att=1.0/(gl_LightSource[i].constantAttenuation+
gl_LightSource[i].linearAttenuation*dist+
gl_LightSource[i].quadraticAttenuation*dist*dist);
}
vec4ambient=gl_FrontLightProduct[i].ambient;
vec4diffuse=clamp(att*NdotL*gl_FrontLightProduct[i].diffuse,0,1);
color+=att*(ambient+diffuse);
}
}
vec4textureColor=texture2D(textureUnit,vec2(gl_TexCoord[0]));
gl_FragColor=TexColor*textureColor+gl_FrontLightModelProduct.sceneColor+color;
}
IsetTexColorto(0.3,0.3,0.3,1.0)andtakescreenshots:
Screenshot
ThereislittlebitlightingwhenIrotatecameraandlighttoleft,
butwhenIrotatetorighttheplanegotfullyilluminated.Ithinkthereissomethingwrongbecausewithoutnormalmappingplanelookssamefromtosides.Hereisnormaltexture.Thanksinadvance.
NormalMap:
openglglslfragment-shadervertex-shader
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editedJun20,2020at9:12
CommunityBot
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askedMar13,2015at22:13
haksisthaksist
20922goldbadges55silverbadges1616bronzebadges
8
IthoughtthatthesenormalsforeveryfragmentandIjustneedtotransformthesenormalstoworldspacetomultiplywithlightdirectiontogetdiffuseintensity
– haksist
Mar14,2015at9:03
1
No,thatwouldworkofthenormalswerestoredinobject-space,buttheyarenot.Thosenormalsareintangent-space,andyoucantellthisbecausethepredominantcolorisblue.Youhavetwooptionshere:1.transformallofyourlightingdirectionvectorsintotangent-spaceor2.reversetransformyournormalmapfromtangent-spacebacktoview-space.BothrequiretheconstructionofaTBNmatrix.
– AndonM.Coleman
Mar14,2015at9:41
Okaythanks.Iwilltry
– haksist
Mar14,2015at9:44
Itriedyoursuggestedsolutionandhereistheresulti1300.photobucket.com/albums/ag94/haksist/….Isittrue?
– haksist
Mar14,2015at13:18
Thatlooksaboutright,it'shardtosaywithoutknowingexactlywherethelightislocated.Colorsarewashedout,butthatwasalreadythecaseinyouroriginalscreenshot.
– AndonM.Coleman
Mar14,2015at13:35
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5
Thatnormalmapisintangent-space,butyouaretreatingitasobject-space.
Youneedabitangentand/ortangentvectorper-vertexinadditiontoyournormalinordertoformthebasistoperformtransformationintoandoutoftangent-space.ThismatrixisoftenreferredtoassimplyTBN.
Youhavetwooptionshere:
Transformallofyourlightingdirectionvectorsintotangent-space
Usefulforforward-shading,canbedoneinavertexshader
Transformyournormalmapfromtangent-spacebacktoview-space
Requiredbydeferred-shading,mustbedoneinfragmentshader
BothoptionsrequiretheconstructionofaTBNmatrix,andifyourtangent-spacebasisisorthogonal(modelingsoftwarelikeAssimpcanbeconfiguredtodothisforyou)youcantransposetheTBNmatrixtodoeitherone.
Youareimplementingforward-shading,sosolution#1istheapproachyoushouldtake.
Belowisaroughoverviewofthenecessarystepsforsolution#1.Ordinarilyyouwoulddothecalculationofthelightingdirectionvectorinthevertexshaderforbetterperformance.
VertexShadertoTransformofLightingVectorsintoTangent-space:
attributevec3tangent;
attributevec3bitangent;
varyingvec3N;
varyingvec3V;
varyingvec3E;
varyingvec3T;
varyingvec3B;
voidmain()
{
N=normalize(gl_NormalMatrix*gl_Normal);
V=vec3(gl_ModelViewMatrix*gl_Vertex);
E=normalize(-V);
T=normalize(gl_NormalMatrix*tangent);
B=normalize(gl_NormalMatrix*bitangent);
gl_TexCoord[0]=gl_MultiTexCoord0;
gl_Position=gl_ModelViewProjectionMatrix*gl_Vertex;
}
FragmentShadertoTransformLightingVectorsintoTangent-space:
varyingvec3N;
varyingvec3V;
varyingvec3E;
varyingvec3B;
varyingvec3T;
uniformsampler2DtextureUnit;
uniformsampler2DnormalTextureUnit;
uniformvec4TexColor;
#defineMAX_LIGHTS1
voidmain()
{
//ConstructTangentSpaceBasis
mat3TBN=mat3(T,B,N);
vec3normal=normalize(texture2D(normalTextureUnit,gl_TexCoord[0].st).xyz*2.0-1.0);
vec4color=vec4(0,0,0,0);
for(inti=0;i0?lightPos.xyz-V:lightPos;
L*=TBN;//Transformintotangent-space
floatdist=length(L);
L=normalize(L);
floatNdotL=max(dot(L,N),0.0);
if(NdotL>0)
{
floatatt=1.0;
if(lightPos.w>0)
{
att=1.0/(gl_LightSource[i].constantAttenuation+
gl_LightSource[i].linearAttenuation*dist+
gl_LightSource[i].quadraticAttenuation*dist*dist);
}
vec4diffuse=clamp(att*NdotL*gl_FrontLightProduct[i].diffuse,0,1);
color+=att*gl_FrontLightProduct[i].ambient+diffuse;
}
}
vec4textureColor=texture2D(textureUnit,vec2(gl_TexCoord[0]));
gl_FragColor=TexColor*textureColor+gl_FrontLightModelProduct.sceneColor+color;
}
Thereisatutorialherethatshouldfillinthegapsandexplainhowtocomputetangentandbitangent.
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editedMar14,2015at14:26
answeredMar14,2015at10:04
AndonM.ColemanAndonM.Coleman
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1
WhatislightPos.wandhowcanIobtainit?
– Nolesh
May20,2019at13:31
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Substance Painter normal map format