From 17dc0febb17888015be1e4ad1ed4b096a4909865 Mon Sep 17 00:00:00 2001 From: Travis CI <zmoelnig@travis-ci.umlaeute.mur.at> Date: Thu, 19 Mar 2015 20:12:11 +0000 Subject: Gem 206d71791bc3642e8c5391a4c59c30ba7411fab8 osx/i386 built 'master:206d71791bc3642e8c5391a4c59c30ba7411fab8' for osx/i386 --- Gem/manual/Lighting.html | 107 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 107 insertions(+) create mode 100644 Gem/manual/Lighting.html (limited to 'Gem/manual/Lighting.html') diff --git a/Gem/manual/Lighting.html b/Gem/manual/Lighting.html new file mode 100644 index 0000000..dcff171 --- /dev/null +++ b/Gem/manual/Lighting.html @@ -0,0 +1,107 @@ +<!doctype html public "-//w3c//dtd html 4.0 transitional//en"> +<html> +<head> + <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> + <meta name="Author" content="Mark Danks"> + <meta name="Author" content="IOhannes m zm�lnig"> + <title>Lighting</title> +</head> +<body> + +<center> +<h2> +<u>Lighting</u></h2></center> +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. +<p>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. +<p>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. +<p>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. +<p><a href="#Activate">Activate lighting</a> +<br><a href="#world_light">[world_light]</a> - A directional light +<br><a href="#light">[light]</a> - A point light in the world +<br><a href="#Moving">Moving lights</a> +<p><img SRC="tribar.gif" height=13 width=561> +<h3> +<a NAME="Activate"></a>Activate lighting</h3> +Lighting is activated by sending a message to <i>[gemwin]</i>. 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. +<p>Individual lights can be turned on and off by sending a 1 or 0 to the +left inlet of the light object itself. +<p><img SRC="tribar.gif" height=13 width=561> +<h3> +<a NAME="world_light"></a>[world_light]</h3> +A <i>[world_light]</i> 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 <i>[world_light]</i> +is good for objects like the sun and other lighting affects. This +means that translating a <i>[world_light]</i> has no effect, although rotation +does. +<p>The following patch is 03.lighting/01.world_light.pd. +<center> +<p><img SRC="world_light.jpg" BORDER=1 height=152 width=370></center> + +<p>The <i>[world_light]</i> has one extra inlet. The right inlet accepts +three floats to set the color of the light. A <i>[color]</i> object +would do nothing. In this case, the light is being set to purple. +The <i>[world_light]</i> also accepts a debug message. The debug message +turns on and off a graphical representation of the light in the scene. +The <i>[world_light]</i> 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. +<p><img SRC="tribar.gif" height=13 width=561> +<h3> +<a NAME="light"></a>[light]</h3> +A <i>[light]</i> 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 <i>[world_light]</i>, +you can translate the <i>[light]</i> object. +<p>Below is the patch 03.lighting/02.light.pd. +<center> +<p><img SRC="light.jpg" BORDER=1 height=215 width=212></center> + +<p>The <i>[light]</i> object has a right inlet for the color, just light +the <i>[world_light]</i> object. As this patch shows, the light can +be moved around the scene with both <i>[rotate]</i> and <i>[translate]</i> +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 <i>[light]</i> +object does not have any size. It exists as a point source. +<p><img SRC="tribar.gif" height=13 width=561> +<h3> +<a NAME="Moving"></a>Moving lights</h3> +The patch 03.lighting/03.controlLights.pd allows you to move a <i>[light]</i> +and <i>[world_light]</i> object in the same scene to see the difference between +the two objects. +<p>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. +<p>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. +<p><img SRC="tribar.gif" height=13 width=561> +<p><a href="index.html">[return]</a> +<br> +</body> +</html> -- cgit v1.2.1