Shadow(阴影).Shadow- Shadows are important elements in creatingrealistic images and in providing the user withvisualcues(暗示)aboutobjectplacementroblempresent
Shadow ( Shadow (阴影) • Shadow – Shadows are important elements in creating realistic imag pg es and in providing the user with visual cues(暗示) about object placement. – Shadow generation is a fundamental problem Shadow generation is a fundamental problem in Computer Graphics. Today, we will present the most important real-time shadow algorithms
ShadowWhyis shadowimportant?- Let's see an example
Shadow • Why is shadow important? – Let’s see an example
ShadowWhyis shadow important?- Do you know where are the balls located?(Without shadows)-It is hard to determine the actual positionO0O
Shadow • Why is shadow important? – Do you know where are the balls located? ( ) Without shadows) – It is hard to determine the actual position
ShadowWhyis shadowimportant?-We know where the balls located are(With shadows)QQ
Shadow • Why is shadow important? – We know where the balls located are ( ) With shadows)
Shadow.Whyis shadowimportant?-Different shadows implies different ballslocation福OO
Shadow • Why is shadow important? – Different shadows implies different balls location
Shadow.Why is shadow important?-From this example, we could conclude that:? Shadows give an important visual cue of objectposition.Same images with different shadows impliesdifferentobjectpositions.- So, shadow is important
Shadow • Why is shadow important? – From this example, we could conclude that: • Shadows gp j ive an important visual cue of object position. • Same images with different shadows implies Same images with different shadows implies different object positions. – S hd i i So, shadow is important
ShadowWhatisShadow?-Definition and Terminations. Consider a light source L illuminating a scene:receiversareobjects ofthescenethatarepotentially illuminated by L.ApointPof the sceneisconsideredtobeintheumbra(本影 if it can not see any part ofL.. IfP can see a part of the light source, it is in thepenumbra(半影)
Shadow • What is Shadow? – Definition and Terminations • Consider a light source L illuminating a scene: • receivers are objects of the scene that are py y otentially illuminated by L. • A point P of the scene is considered to be in the umbra(本影) if it can not see any part of L. if it can not see any part of L. • If P can see a part of the light source, it is in the penumbra(半影)
ShadowWhatisShadow?-Definition and Terminations·Shadow is the union of the umbra (本影 andthe penumbra (半影, is the region of spacefor which at least one point of the lightsourceis occluded.. Objects that hide a point from the lightsourceare calledoccluders(遮档物)
Shadow • What is Shadow? – Definition and Terminations • Shadow is the union of the umbra is the union of the umbra (本影) and the penumbra (半影), is the region of space f hi h l i f h li h for which at least one point of the light source is occluded. • Objects that hide a point from the light source are call de occld ( u ers 遮挡物)
ShadowWhatis Shadow?LightSource-Definitionand TerminationsOccluderRecieverpenumbrapenumbraUmbra
Shadow • What is Shadow? D fi iti Light Source – Definition and Terminations g Occluder b penumbra Reciever Umbra penum ra penumbra
ShadowTypesofShadows- attached shadows: occurring when the normal ofthe receiver is facing away from the light source;-cast shadows: occurring when a shadow falls onan object whose normalis facingtowardthelightsource.-Self-shadows: are a specific case of cast shadowsthat occur when the shadow of an objectisprojected onto itself, i.e. the occluder and thereceiver are the same
Shadow • Types of Shadows – attached shadows attached shadows: occurring when the normal of : occurring when the normal of the receiver is facing away from the light source; – cast hd s a ows: occurri h h d f ll ing when a shadow falls on an object whose normal is facing toward the light source. – Self-shadows: are a specific case of cast shadows th t h th h d f bj t i that occur when the shadow of an object is projected onto itself, i.e. the occluder and the receiver are the same receiver are the same