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brazil:lightoptions [2016/03/24]
sandy
brazil:lightoptions [2016/03/29] (current)
sandy
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-All these can be translated into Brazil light types. Unfortunately,​ there is no 1-to-1 correlation,​ partly because Brazil lights are far more flexible and not as limited to a kind of base light geometry. In fact, a single light object in Brazil can behave as a rectangular light when it comes to emitting photons but it can behave as a pointlight when it comes to casting shadows. There'​s a lot to learn about lighting in Brazil and it's an important topic, you need to learn the basics if you expect to make well balanced images.+All these can be translated into Brazil light types. Unfortunately,​ there is no 1-to-1 correlation,​ partly because Brazil lights are far more flexible and not as limited to a kind of base light geometry. In fact, a single light object in Brazil can behave as a rectangular light when it comes to emitting photons but it can behave as a pointlight when it comes to casting shadows. There'​s a lot to learn about lighting in Brazil and it's an important topic. You need to learn the basics if you expect to make well balanced images.
  
  
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 | {{:​legacy:​en:​Brazil_PointLightStandard.png}} | {{:​legacy:​en:​Brazil_PointLightTargetRadius.png}} | {{:​legacy:​en:​Brazil_PointLightTargetRadiusAttenuation.png}} | | {{:​legacy:​en:​Brazil_PointLightStandard.png}} | {{:​legacy:​en:​Brazil_PointLightTargetRadius.png}} | {{:​legacy:​en:​Brazil_PointLightTargetRadiusAttenuation.png}} |
-| When we add a regular point light to a model, we get a light with default properties (no shadows, no focus, no target, no decay, no attenuation,​ no projection, no photon maps, no nothing, except for a color and a brightness). It looks just like a normal Rhino point light and it behaves in the same way. | All light objects in Brazil can have a target associated with them. In the image above this target has been specified. A target essentially defines a direction for the light. In Rhino it doesn'​t make sense to have a direction for a point light which, by definition, shines in all directions. But with the Brazil'​s added features, we need to specify a target. Also, this screenshot shows the Radius value of this particular light. | Another Brazil light property which has no precedent in Rhino is attenuation. Attenuation controls the influence of a light object as a function of distance, but it is not a physical ​correct falloff like Decay. Attenuation is defined by four radii values in which each is represented by a partial sphere. |+| When we add a regular point light to a model, we get a light with default properties (no shadows, no focus, no target, no decay, no attenuation,​ no projection, no photon maps, no nothing, except for a color and a brightness). It looks just like a normal Rhino point light and it behaves in the same way. | All light objects in Brazil can have a target associated with them. In the above image this target has been specified. A target essentially defines a direction for the light. In Rhino it doesn'​t make sense to have a direction for a point light which, by definition, shines in all directions. But with the Brazil'​s added features, we need to specify a target. Also, this screenshot shows the Radius value of this particular light. | Another Brazil light property which has no precedent in Rhino is attenuation. Attenuation controls the influence of a light object as a function of distance, but it is not a physically ​correct falloff like Decay. Attenuation is defined by four radii values in which each is represented by a partial sphere. |
 | {{:​legacy:​en:​Brazil_PointLightFocus.png}} | {{:​legacy:​en:​Brazil_RectAreaLightFocus.png}} | {{:​legacy:​en:​Brazil_CircAreaLightFocus.png}} | | {{:​legacy:​en:​Brazil_PointLightFocus.png}} | {{:​legacy:​en:​Brazil_RectAreaLightFocus.png}} | {{:​legacy:​en:​Brazil_CircAreaLightFocus.png}} |
-| Brazil does not distinguish between point and spotlights, which may come as a surprise to old school Rhino users. In Brazil, a point light with a focus automatically becomes a spotlight. This screenshot shows the same light as before (originally a point light), but with a specific focus. Now we see why it is important for pointlights ​to have a target direction, it defines where the focal cones are pointing. [[#Focus]] is defined by an inner and outer radius, called Hotspot and Falloff respectively. | An area light has a different geometry than a point light, and thus the shape of the focus cones is different. Brazil lights by default use the same shape for the focus and shadow properties as the light geometry, but you can override these to be anything you like. | Another type of area light in Brazil (one which does not exist in Rhino) is the circular area light. Again, it results in a different focus cone. |+| Brazil does not distinguish between point and spotlights, which may come as a surprise to old school Rhino users. In Brazil, a point light with a focus automatically becomes a spotlight. This screenshot shows the same light as before (originally a point light), but with a specific focus. Now we see why it is important for point lights ​to have a target direction, it defines where the focal cones are pointing. [[#Focus]] is defined by an inner and outer radius, called Hotspot and Falloff respectively. | An area light has a different geometry than a point light, and thus the shape of the focus cones is different. Brazil lights by default use the same shape for the focus and shadow properties as the light geometry, but you can override these to be anything you like. | Another type of area light in Brazil (one which does not exist in Rhino) is the circular area light. Again, it results in a different focus cone. |
 | {{:​legacy:​en:​Brazil_DirectionalLightFocusAttenuation.png}} | {{:​legacy:​en:​Brazil_DirectionalLightFocus.png}} |       | | {{:​legacy:​en:​Brazil_DirectionalLightFocusAttenuation.png}} | {{:​legacy:​en:​Brazil_DirectionalLightFocus.png}} |       |
-| Even directional lights (called '​parallel'​ in Brazil ​terminology) can have focus and attenuation associated with them. Here we see a cylindrical focus... | ...and here a point focus property. |       |+| Even directional lights (called '​parallel'​ in Brazil) can have focus and attenuation associated with them. Here we see a cylindrical focus... | ...and here a point focus property. |       |
  
  
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 ====Point lights==== ====Point lights====
  
-| {{:​legacy:​en:​Brazil_PointLight.jpg}} |  Point lights are simple entities, they emit light equally in all directions. You can change this behavior by assigning a focus value to a point light, turning it into a spot light. See the section on [[#Focus]] for more details. This point light has been given a sphere-area radius, making the shadows soft.  |+| {{:​legacy:​en:​Brazil_PointLight.jpg}} |  Point lights are simple entities. They emit light equally in all directions. You can change this behavior by assigning a focus value to a point light, turning it into a spot light. See the section on [[#Focus]] for more details. This point light has been given a sphere-area radius, making the shadows soft.  |
  
  
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 ====Area lights==== ====Area lights====
  
-| {{:​legacy:​en:​Brazil_AreaLight.jpg}} |  Area lights, either circular or rectangular,​ are far more computationally expensive ​that point or parallel lights. Instead of a single coordinate, Brazil has to solve the exposure of a certain part of the 3D scene for a finite surface. The resulting image is also likely to contain more grain or noise. However, area lights give a far more realistic lighting. A special case of area lights are light portals, which have the same shape as area lights but instead of emitting light they channel existing light. ​ |+| {{:​legacy:​en:​Brazil_AreaLight.jpg}} |  Area lights, either circular or rectangular,​ are far more computationally expensive ​than point or parallel lights. Instead of a single coordinate, Brazil has to solve the exposure of a certain part of the 3D scene for a finite surface. The resulting image is also likely to contain more grain or noise. However, area lights give a far more realistic lighting. A special case of area lights are light portals, which have the same shape as area lights but instead of emitting light they channel existing light. ​ |
  
  
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 | {{:​legacy:​en:​Brazil_IndirectBalls.jpg}} |  Since Brazil is capable of Global illumination (GI) lighting you can theoretically use glowing geometry instead of light sources. Non-biased render engines such as Maxwell Render and Fry Render use this approach which means that **A** the resulting lighting is very realistic and **B** the process of solving these images is slow. Also, there is almost nothing you can do to tweak the behavior of light in GI only scenes, things just happen like they would in the real world. The scene on the left contains several very bright, but colored balls. Since the decay of these light sources is physically correct, we get very intense little islands of brightness which may be undesirable. ​ | {{:​legacy:​en:​Brazil_IndirectBalls.jpg}} |  Since Brazil is capable of Global illumination (GI) lighting you can theoretically use glowing geometry instead of light sources. Non-biased render engines such as Maxwell Render and Fry Render use this approach which means that **A** the resulting lighting is very realistic and **B** the process of solving these images is slow. Also, there is almost nothing you can do to tweak the behavior of light in GI only scenes, things just happen like they would in the real world. The scene on the left contains several very bright, but colored balls. Since the decay of these light sources is physically correct, we get very intense little islands of brightness which may be undesirable. ​
  
-The four images below are other examples of GI only lighting. The bright column has a brightness of 1.0, 2.0 and 10.0 respectively and the light can bounce three times before the sampler terminates. The final image uses a [[http://​en.wikipedia.org/​wiki/​Subsurface_scattering|Wax]] ​ material instead of a Lambert, ​  ​meaning the GI lighting also propagates //through// the blocks instead of just bouncing off the walls. Some of the light escapes through the top faces of the columns, something which is not possible with completely opaque materials. ​|+The four images below are other examples of GI only lighting. The bright column has a brightness of 1.0, 2.0 and 10.0 respectively and the light can bounce three times before the sampler terminates. The final image uses a [[http://​en.wikipedia.org/​wiki/​Subsurface_scattering|Wax]] ​ material instead of a Lambert, ​  ​meaning the GI lighting also propagates //through// the blocks instead of just bouncing off the walls. Some of the light escapes through the top faces of the columns, something which is not possible with completely opaque materials. ​
  
 | {{:​legacy:​en:​Brazil_IndirectGI_1.png}} | {{:​legacy:​en:​Brazil_IndirectGI_2.png}} | {{:​legacy:​en:​Brazil_IndirectGI_10.png}} | {{:​legacy:​en:​Brazil_IndirectGISSS_10.jpg}} | | {{:​legacy:​en:​Brazil_IndirectGI_1.png}} | {{:​legacy:​en:​Brazil_IndirectGI_2.png}} | {{:​legacy:​en:​Brazil_IndirectGI_10.png}} | {{:​legacy:​en:​Brazil_IndirectGISSS_10.jpg}} |
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 | Area shadows take into account the size of the light source and compute a shadow according to the amount of obstruction of this source. The shape of the light source is defined by geometry (rectangle, circle or sphere) and size (in model units). (See the section below this table for an explanation of area shadows.) The image above was made with a spherical light source with a radius of 1.0 unit. | This time the radius of the sphere has been increased to 10.0 units. These images show how shadow edges become more fuzzy as the distance from the edge to the obstructing object increases. | | Area shadows take into account the size of the light source and compute a shadow according to the amount of obstruction of this source. The shape of the light source is defined by geometry (rectangle, circle or sphere) and size (in model units). (See the section below this table for an explanation of area shadows.) The image above was made with a spherical light source with a radius of 1.0 unit. | This time the radius of the sphere has been increased to 10.0 units. These images show how shadow edges become more fuzzy as the distance from the edge to the obstructing object increases. |
 | {{:​legacy:​en:​Brazil_AreaLight_AreaShadows.jpg}} | {{:​legacy:​en:​Brazil_AreaLight_Vertical.jpg}} | | {{:​legacy:​en:​Brazil_AreaLight_AreaShadows.jpg}} | {{:​legacy:​en:​Brazil_AreaLight_Vertical.jpg}} |
-| If we use a rectangular light source shape, the resulting patches get a bit messier. Since the holes in our wall are fairly small, they act as pinhole cameras, projecting an inverse of the lightsource ​onto the groundplane. They are not small enough for an accurate projection though so we are left with splotches halfway between circles and rectangles. | If we use a unsquare rectangle though, the difference becomes striking. Here, the light source is a very thin, but very high rectangle, which means the amount of horizontal blurring is minimal (the light is thin enough in this direction to resemble a sharp shadow) while vertical blurring is through the roof. |+| If we use a rectangular light source shape, the resulting patches get a bit messier. Since the holes in our wall are fairly small, they act as pinhole cameras, projecting an inverse of the light source ​onto the groundplane. They are not small enough for an accurate projection though so we are left with splotches halfway between circles and rectangles. | If we use a unsquare rectangle though, the difference becomes striking. Here, the light source is a very thin, but very high rectangle, which means the amount of horizontal blurring is minimal (the light is thin enough in this direction to resemble a sharp shadow) while vertical blurring is through the roof. |
  
  
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 ====Decay and attenuation==== ====Decay and attenuation====
  
-source of light in the real world (the sun, say) emits a certain amount of photons per time interval. The added energy of all these photons totals the brightness of the star. Since all light particles travel at the same speed, all the photons that left the surface of the sun at 7 o'​clock in the morning will have travelled about 300 million meters in all directions during the first second. They now define a sphere with a total surface area of 3×10^17^ square meters, indicated by the orange semi-sphere in the left picture. Three seconds later the total surface area of the photon wavefront is about 4.5×10^18^ square meters (the orange semi-sphere in the right image) which is effectively 15 times larger. Yet the total number of photons hasn't changed, meaning that the larger sphere has a much lower light //density// than the smaller sphere. Since we are talking about a surface area (//square// meters), the speed at which light becomes weaker is proportional to the inverse //square// of the distance travelled. This is called **decay** and all radiating light in the physical universe obeys this rule. (Laser for example does not, since all photons are travelling along parallel paths).+A light source ​in the real world (such as the sun) emits a certain amount of photons per time interval. The added energy of all these photons totals the brightness of the star. Since all light particles travel at the same speed, all the photons that left the surface of the sun at 7 o'​clock in the morning will have travelled about 300 million meters in all directions during the first second. They now define a sphere with a total surface area of 3×10^17^ square meters, indicated by the orange semi-sphere in the left picture. Three seconds later the total surface area of the photon wavefront is about 4.5×10^18^ square meters (the orange semi-sphere in the right image) which is effectively 15 times larger. Yet the total number of photons hasn't changed, meaning that the larger sphere has a much lower light //density// than the smaller sphere. Since we are talking about a surface area (//square// meters), the speed at which light becomes weaker is proportional to the inverse //square// of the distance travelled. This is called **decay** and all radiating light in the physical universe obeys this rule. (Laser for example does not, since all photons are travelling along parallel paths).
  
  
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 | {{:​legacy:​en:​Brazil_NoDecay.jpg}} | {{:​legacy:​en:​Brazil_InverseDecay.jpg}} | {{:​legacy:​en:​Brazil_InverseSquareDecay.jpg}} | | {{:​legacy:​en:​Brazil_NoDecay.jpg}} | {{:​legacy:​en:​Brazil_InverseDecay.jpg}} | {{:​legacy:​en:​Brazil_InverseSquareDecay.jpg}} |
-| The default for lights in Brazil is not to have decay enabled. The torus in the above image is lit by a sky light and a single point light without decay. The fact that the groundplane near the point light location is brighter than the groundplane near the edges of the image, has got nothing to do with decay, but is a result of the Lambertian shading. Lumberton shading states that surfaces which are lit perpendicularly are brighter than surfaces which are lit at an angle. | When we enable decay for the point light, the brightness of the overall image decreases significantly. In this case, the decay is not inverse square but inverse linear, which is not physically correct. But because inverse square decay tends to be extremely sharp, we have this option. Note how the far end of the torus is much darker, even though it is lit perpendicularly. | Finally, inverse square decay. I had to pump up the brightness of the light source to 5.0 or nothing was visible in this scene, which is a testament to the strength of the brightness decay in inverse square setups. |+| The default for lights in Brazil is not to have decay enabled. The torus in this image is lit by a sky light and a single point light without decay. The fact that the groundplane near the point light location is brighter than the groundplane near the edges of the image, has got nothing to do with decay, but is a result of the Lambertian shading. Lumberton shading states that surfaces which are lit perpendicularly are brighter than surfaces which are lit at an angle. | When we enable decay for the point light, the brightness of the overall image decreases significantly. In this case, the decay is not inverse square but inverse linear, which is not physically correct. But because inverse square decay tends to be extremely sharp, we have this option. Note how the far end of the torus is much darker, even though it is lit perpendicularly. | Finally, inverse square decay. I had to pump up the brightness of the light source to 5.0 or nothing was visible in this scene, which is a testament to the strength of the brightness decay in inverse square setups. |
  
  
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-Another method of controlling the brightness of a light source at a distance is attenuation. This, too, is a physically incorrect effect, but it can come in handy when a scene is over-exposed and you need darken it. Attenuation is like focus, except that the brightness gradient is specified by distance rather than angle. With attenuation you can control both the fade-in and fade-out luminance gradients:+Another method of controlling the brightness of a light source at a distance is attenuation. This, too, is a physically incorrect effect, but it can come in handy when a scene is over-exposed and you need to darken it. Attenuation is like focus, except that the brightness gradient is specified by distance rather than angle. With attenuation you can control both the fade-in and fade-out luminance gradients:
  
  
  
 | {{:​legacy:​en:​Brazil_AttenuationFar.jpg}} |  {{:​legacy:​en:​Brazil_AttenuationNear.jpg}} | {{:​legacy:​en:​Brazil_AttenuationBoth.jpg}} | | {{:​legacy:​en:​Brazil_AttenuationFar.jpg}} |  {{:​legacy:​en:​Brazil_AttenuationNear.jpg}} | {{:​legacy:​en:​Brazil_AttenuationBoth.jpg}} |
-| Here, the fade-out attenuation has been set. The distances that define the fade-out domain are very close together, accentuating the physical incorrectness of the effect. | This time fade-in attenuation only.  | And both combined. |+| Here, the fade-out attenuation has been set. The distances that define the fade-out domain are very close together, accentuating the physical incorrectness of the effect. | Fade-in attenuation only.  | And both combined. |
  
  
brazil/lightoptions.txt · Last modified: 2016/03/29 by sandy