Re: [Algorithms] Deferred shadow mask generation
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From: Wolfgang E. <wol...@gm...> - 2007-04-06 06:30:48
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<<< If so, how do you avoid the typical "halo" effect when using such a techniq= ue? <<< Yes I actively ignore it :-) On 4/5/07, Francis Boivin <fra...@ub...> wrote: > > Are you also blurring the Shadow collector texture afterwards to get > smoother looking shadows? If so, how do you avoid the typical "halo" eff= ect > when using such a technique? > ________________________________ > From: gda...@li... > [mailto:gda...@li...] On > Behalf Of Wolfgang Engel > Sent: Thursday, April 05, 2007 11:42 AM > > To: 'Game Development Algorithms' > Subject: Re: [Algorithms] Deferred shadow mask generation > > > > > <<< > > Now render all gathered Shadowmap in a preprocess (Deferred Shadowing) -> > Shadow collector > > Render each Shadowmap collected from the viewer point of view and stor= e > the shadow factor in a screen-sized texture > > Render Cascaded Shadowmap (Put the 4 light space matrix in constant > register and select the right light projection to use via compare/dot > product) > > And store the shadow factor=85 > > <<< > > You can render the four maps into the shadow collector in one pass. > > You just fetch the shadow collector then as a screen-space texture for ea= ch > object ... e.g. you use the vpos register in the pixel shader or calculat= e > the screen space position in the vertex shader. > > > > So overall five render passes: four to create the shadow maps, one into t= he > shadow collector and the one in the shadow collector is also the Z pre-pa= ss. > > > > <<< > > When you said to store shadow factor in r, g or b channel, you mean that = the > different shadow factor must not be blend together and should be left > separated > > Until they are use for lighting calculation ? So in the above description= , > spot light should be render in r channel and cascaded in g, then at light= ing > do two texture fetch ? > > <<< > > You might want to use different colors for different shadows. Cloud shado= ws > should be more faint and the shadows casted by objects on the ground > stronger. > > > > Z pre-pass: you have to render like this anyway, why not just use the sha= dow > collector pass for this :-) > > > > - Wolfgang > > > > > > > > > From: gda...@li... > [mailto:gda...@li...] On > Behalf Of Lagarde S=E9bastien > Sent: Thursday, April 05, 2007 1:26 AM > To: 'Game Development Algorithms' > Subject: Re: [Algorithms] Deferred shadow mask generation > > > > Alright, I have checked your article and the paper mentioned (PSSM), than= ks > for the pointer. > > > > So If I have well understood: > > > > In a first time you render all the shadowmap for your game: > > Render Shadowmap for projected ligt > > Render Shadowmap for omni light with cubemap or multiple frustum > > Etc=85 > > Render Cascaded Shadowmap for the sun light (with day and light cycle > managed): > > Here for the directional light representing the Sun > > you render 4 Shadowmap for each 4 frustum slice transformed in light > space in one texture (aka texture atlas) > > > > Now render all gathered Shadowmap in a preprocess (Deferred Shadowing) -> > Shadow collector > > Render each Shadowmap collected from the viewer point of view and stor= e > the shadow factor in a screen-sized texture > > Render Cascaded Shadowmap (Put the 4 light space matrix in constant > register and select the right light projection to use via compare/dot > product) > > And store the shadow factor=85 > > > > When you said to store shadow factor in r, g or b channel, you mean that = the > different shadow factor must not be blend together and should be left > separated > > Until they are use for lighting calculation ? So in the above description= , > spot light should be render in r channel and cascaded in g, then at light= ing > do two texture fetch ? > > And I not understand why shadow collector is the z-prepass, don't you nee= d > to do a z-prepass before to render in the shadow collector, > > You can save a lot of compare and texture fetch or I missed something ? > > > > Thanks for your help. > > > > Lagarde S=E9bastien > > Software engineer > > Neko entertainment > > > > > ________________________________ > > > De : gda...@li... > [mailto:gda...@li...] De > la part de Wolfgang Engel > Envoy=E9 : mercredi 4 avril 2007 14:34 > =C0 : 'Game Development Algorithms' > Objet : Re: [Algorithms] Deferred shadow mask generation > > > > Oh and the shadow collector pass is the Z pre-pass =85 > > > > > From: gda...@li... > [mailto:gda...@li...] On > Behalf Of Lagarde S=E9bastien > Sent: Wednesday, April 04, 2007 4:55 AM > To: gda...@li... > Subject: [Algorithms] Deferred shadow mask generation > > > > Hello, > > I heard that the Crytech engine2 use a specific technique they call > "deferred shadow mask generation" for blend all shadow buffer in one shad= ow > buffer > > Then practice a "smart blur" on it to get soft shadows. > > This mask is then reuse later to render shadow in the scene. > > > > Anyone heard about a similar technique like this or have some information= on > how to gather many shadow buffer in one ? > > > > Thank you. > > > > Lagarde S=E9bastien > > Software engineer > > Neko entertainment > > > > > ------------------------------------------------------------------------- > Take Surveys. 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