So I modelled a quick little street light and just need a basic spot light to illuminate the ground, but i cant seem to figure out how to make the like not eminate from a pinhead. Since the light needs to eminate from the same size as the lamp im having trouble.
You’re looking to set the start of the Halo effect on your spot lamp, correct? As far as I know, there’s not really a setting for this… though it would be useful.
As a work around, you could create a mesh in the shape of the light cone and fake at least the start of the beam with blend texture and just use the lamp (minus the halo) as a source of illumination.
@RickyBlender: He did provide a drawing. He wants to use a spot lamp with a halo effect for the look of volumetric lighting coming from the street light… but when you do this, the halo starts at the light source rather than the Clip Start of the spot… giving you the full cone. Unfortunately, there’s not a way to directly do this from within Blender, so he’ll have to use a work-around.
Yeah Fweeb has it spot on. Unfortunately I think he’s right. I tried using some node networks & such to get the effect, but it didnt work. Maybe a solid mesh with a halo material a looooooowww transpaency?
I wonder if there would be a way to make the light up high in a separate image, but with the part above and inside the opaque parts of the street light masked out. Then composite it together with the street light image…
Easier if the project is to result in a still image, not so easy if it’s for a detailed animation.
best thing i can think of is create a rectangular area light inside the glass and make the glass transparent…
that or use an external renderer that supports illuminating objects
I hadnt tried a rect light, but i dont think that accomidates visible light (fog) does it?
this will end up being a light rig for some industrial animations im working on, so the masking idea is out. I was trying similar ideas with nodes, but cant seem to get it to work.
You can do it with nodes. I’ve attached a .blend file to show how. Basically, there are two render layers: one with the lamp object and one that has the halo and a mask object. Set the mask object’s material to have an alpha of zero, but leave ztransparency turned off. Then you combine them with a simple alpha-over. See the attached blend and it’ll make sense.
The process is pretty simple. Basically, it uses (abuses?) the way Blender handles a material’s alpha value. There are three ways: z-transparency, ray transparency, and neither z nor ray. Enabling z or ray will let you see through the material to other objects in the scene (like you would normally want when you make a material transparent). However, if you don’t enable either of these, then the material doesn’t show objects behind it; it only shows the background (basically the Sky in the World buttons). This may appear pretty useless at first, but you can actually take advantage of this behavior and create what amounts to a 3D mask.
Here’s a step-by-step of exactly what I did in the above .blend file:
Create an Icosphere, delete the upper half of it, and extrude/scale the top ring of vertices to put a cap on it (btw, I forgot to remove doubles there, but I was in a hurry; cut me a little slack :P)
In the Icosphere’s material settings, I just used the default material with a reduced alpha to give it some transparency (I enabled z-transparency on this object). Also, for kicks, I increased the Emit value of the material so it looks more like light is coming from the Icosphere. This is really a hackish way to do this, though… in a real scene I’d probably just properly light the other side of the icosphere.
Create a Spot lamp and align it so it looks like its rays are coming out of the Icosphere. Enable Halo in the Spot’s light settings.
Create a 10-sided Cone and align it with the top of the Icosphere. I made the Cone 10-sided just to match the number of upper edges on the Icosphere. Not super important, but I guess I’m a little OCD.
Here’s the important bit. Create a new material for the Cone and set the alpha for that material to 0.0 without enabling z-transparency or ray transparency. Also, to ensure no specular highlights or shadows appeared on the Cone, I set the material to Shadeless. In a real situation, I might also disable the shadow buffer for the cone so it doesn’t accidentally cast a shadow on the scene.
At this point, the mask is created. Now it gets used in the compositor. First though, I did a little layer-shuffling. The Icosphere was left on Layer 1 while the Cone and Spot were pushed to Layer 2.
Now for the Render Layers. Set the default Render Layer to just use Layer 1 and then created a second Render Layer (which I named “light”) which only uses Layer 2.
In the Node Compositor, add a new Render Layer node for the light Render Layer and mix the two Render Layers together with an Alpha Over node.
so this simulate a volumetric light cone for the lamp
which you don’t really see in the street normally but more in a theater i guess
unless it’s extremely fogy or snowy or even rainy maybe
nice trick anyway
there is also the trick about the UV and how come when you press on F12 it render
in the vewiport for UV ?
never used that one can you explain it a little
It’s the last button (drop-down) in the Output panel of the Render buttons. You have three choices: Render Window, Image Editor, and Fullscreen. I typically use Fullscreen for my own work, but Image Editor is nice when you want to work on settings or compositing while still seeing your render.
I tend to avoid using Render Window (the default behavior) because I’m not fond of overlapping windows.
This was a very helpful thread.
It at least got me in the ball park for
figuring out lighting in my project.
No there yet, but I’m not making
adjustments so blindly any more just
hoping to see changes.