Lighting

From 9b873693bdcbfe439a4157564ece781f67e58239 Mon Sep 17 00:00:00 2001 From: Travis CI Date: Thu, 9 May 2019 20:35:45 +0000 Subject: Gem 01b1861db023a225d01a4d5a519cf54f09f631f5 linux/amd64 built 'master:01b1861db023a225d01a4d5a519cf54f09f631f5' for linux/amd64 --- Gem/manual/Lighting.html | 214 +++++++++++++++++++++++------------------------ 1 file changed, 107 insertions(+), 107 deletions(-) (limited to 'Gem/manual/Lighting.html') diff --git a/Gem/manual/Lighting.html b/Gem/manual/Lighting.html index dcff171..5c30fb9 100644 --- a/Gem/manual/Lighting.html +++ b/Gem/manual/Lighting.html @@ -1,107 +1,107 @@ - - - - - - - Lighting - - - - -

-Lighting

-Lighting is an important factor is how we perceive the quality of an image. -For example, without lighting and shading, a sphere would just look like -a circle. GEM provides two types of lights, a local light and world -light. -

OpenGL uses a vertex lighting model. This means that for every -vertex in the scene, the influence of the light is calculated. The -color for the polygon is then modified by the light value of all of the -vertices. This generally produces a very smooth effect, but you will -occasionally run into rendering artifacts, especially if you use local -lights. For example, imagine you have a local light close a large -square. The corners of the square are far away from the light, so -none of them will be lit very brightly, even though the light itself is -very close to the surface of the square. -

It is important to realize that lighting is an expensive operation to -use. The number of polygons that you will be able to render will -be much lower if lighting is turned on. As usual, the complexity -of the scene and the speed of your computer and graphics card will greatly -affect your frame rate. -

GEM has only a maximum of 8 lights at one time. If you try to -create more lights than that, you will get an error message. -

Activate lighting -
[world_light] - A directional light -
[light] - A point light in the world -
Moving lights -

-Activate lighting

-Lighting is activated by sending a message to [gemwin]. If you -send "lighting 1", then lighting will be turned on. If you send "lighting -0", then lighting will be turned off. The lighting state is kept -even if you destroy the gemwin. This means that if you close a patch -and open another one, the lighting will still be the same. -

Individual lights can be turned on and off by sending a 1 or 0 to the -left inlet of the light object itself. -

-[world_light]

-A [world_light] is a light which exists infintely far away. -This reduces the computation needed, so your patch can run faster, but -it means that all of the light rays are parallel. The [world_light] -is good for objects like the sun and other lighting affects. This -means that translating a [world_light] has no effect, although rotation -does. -

The following patch is 03.lighting/01.world_light.pd. -

- -

The [world_light] has one extra inlet. The right inlet accepts -three floats to set the color of the light. A [color] object -would do nothing. In this case, the light is being set to purple. -The [world_light] also accepts a debug message. The debug message -turns on and off a graphical representation of the light in the scene. -The [world_light] looks like a cone. The cone shows the direction -that the light is coming from. Remember that the actual position -of the light does not matter, so geos behind the cone will still be lit. -It is the direction of the light that matters. This is why you can -rotate the light. -

-[light]

-A [light] object generates a point light in the world. Because -the light is local to the scene, there is more math to generate the effect -of the light on the vertices. However, unlike a [world_light], -you can translate the [light] object. -

Below is the patch 03.lighting/02.light.pd. -

- -

The [light] object has a right inlet for the color, just light -the [world_light] object. As this patch shows, the light can -be moved around the scene with both [rotate] and [translate] -objects. If you were to set the translate X value equal to 1.0, then -the sphere would not be lit at all. This is because the light would -be inside of the sphere. When you turn on the debug representation, -it is a sphere with its origin where the light it. The [light] -object does not have any size. It exists as a point source. -

-Moving lights

-The patch 03.lighting/03.controlLights.pd allows you to move a [light] -and [world_light] object in the same scene to see the difference between -the two objects. -

The patch 03.lighting/04.moveSpheres.pd is an example which moves -two spheres around the world. Turn on and off the individual lights -for a demonstration of a local versus infinite light. -

The patch 03.lighting/05.materials.pd uses the material objects to -selectively control the color of the object. Notice that the diffuse object -sets the "overall" color, while the specular objects sets the bright reflective -area where the light directly shines. -

[return] -
- - + + + + + + + Lighting + + + +

+Lighting

+Lighting is an important factor is how we perceive the quality of an image. +For example, without lighting and shading, a sphere would just look like +a circle. GEM provides two types of lights, a local light and world +light. +

OpenGL uses a vertex lighting model. This means that for every +vertex in the scene, the influence of the light is calculated. The +color for the polygon is then modified by the light value of all of the +vertices. This generally produces a very smooth effect, but you will +occasionally run into rendering artifacts, especially if you use local +lights. For example, imagine you have a local light close a large +square. The corners of the square are far away from the light, so +none of them will be lit very brightly, even though the light itself is +very close to the surface of the square. +

It is important to realize that lighting is an expensive operation to +use. The number of polygons that you will be able to render will +be much lower if lighting is turned on. As usual, the complexity +of the scene and the speed of your computer and graphics card will greatly +affect your frame rate. +

GEM has only a maximum of 8 lights at one time. If you try to +create more lights than that, you will get an error message. +

Activate lighting +
[world_light] - A directional light +
[light] - A point light in the world +
Moving lights +

+Activate lighting

+Lighting is activated by sending a message to [gemwin]. If you +send "lighting 1", then lighting will be turned on. If you send "lighting +0", then lighting will be turned off. The lighting state is kept +even if you destroy the gemwin. This means that if you close a patch +and open another one, the lighting will still be the same. +

Individual lights can be turned on and off by sending a 1 or 0 to the +left inlet of the light object itself. +

+[world_light]

+A [world_light] is a light which exists infintely far away. +This reduces the computation needed, so your patch can run faster, but +it means that all of the light rays are parallel. The [world_light] +is good for objects like the sun and other lighting affects. This +means that translating a [world_light] has no effect, although rotation +does. +

The following patch is 03.lighting/01.world_light.pd. +

+ +

The [world_light] has one extra inlet. The right inlet accepts +three floats to set the color of the light. A [color] object +would do nothing. In this case, the light is being set to purple. +The [world_light] also accepts a debug message. The debug message +turns on and off a graphical representation of the light in the scene. +The [world_light] looks like a cone. The cone shows the direction +that the light is coming from. Remember that the actual position +of the light does not matter, so geos behind the cone will still be lit. +It is the direction of the light that matters. This is why you can +rotate the light. +

+[light]

+A [light] object generates a point light in the world. Because +the light is local to the scene, there is more math to generate the effect +of the light on the vertices. However, unlike a [world_light], +you can translate the [light] object. +

Below is the patch 03.lighting/02.light.pd. +

+ +

The [light] object has a right inlet for the color, just light +the [world_light] object. As this patch shows, the light can +be moved around the scene with both [rotate] and [translate] +objects. If you were to set the translate X value equal to 1.0, then +the sphere would not be lit at all. This is because the light would +be inside of the sphere. When you turn on the debug representation, +it is a sphere with its origin where the light it. The [light] +object does not have any size. It exists as a point source. +

+Moving lights

+The patch 03.lighting/03.controlLights.pd allows you to move a [light] +and [world_light] object in the same scene to see the difference between +the two objects. +

The patch 03.lighting/04.moveSpheres.pd is an example which moves +two spheres around the world. Turn on and off the individual lights +for a demonstration of a local versus infinite light. +

The patch 03.lighting/05.materials.pd uses the material objects to +selectively control the color of the object. Notice that the diffuse object +sets the "overall" color, while the specular objects sets the bright reflective +area where the light directly shines. +

[return] +
+ + -- cgit v1.2.1