How to use the ZGE-Light component?

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ab2
Posts: 6
Joined: Tue Jan 25, 2022 1:39 pm

How to use the ZGE-Light component?

Post by ab2 »

The documentation is sparse

http://www.zgameeditor.org/index.php/ComponentRef/Light


and I did not find any zgeproj-file nor another tutorial or example
that is using the ZGE-Light component.

Can someone demonstrate the usage?

My attempts to add lights did not change the scene at all.

What would be needed?

Thanks for some advice.

Cheers

Andreas
User avatar
Kjell
Posts: 1876
Joined: Sat Feb 23, 2008 11:15 pm

Re: How to use the ZGE-Light component?

Post by Kjell »

Hi Andreas,
ab2 wrote: Wed Feb 16, 2022 2:43 pmCan someone demonstrate the usage?
Here's a simple demonstration of a white cube being lit by 3 differently colored point lights ( red, green and blue ).

Code: Select all

<?xml version="1.0" encoding="iso-8859-1" ?>
<ZApplication Name="App" Caption="ZGameEditor application" AmbientLightColor="0 0 0 1" FileVersion="2">
  <OnLoaded>
    <SpawnModel Model="Box"/>
  </OnLoaded>
  <OnUpdate>
    <ZExpression>
      <Expression>
<![CDATA[// Animate all 3 lights

float t = App.Time/8;

RedLight.Position.X = cos(t*3)*4;
RedLight.Position.Z = sin(t*3)*4;

GreenLight.Position.Y = cos(t*4)*4;
GreenLight.Position.Z = sin(t*4)*4;

BlueLight.Position.X = cos(t*5)*4;
BlueLight.Position.Y = sin(t*5)*4;]]>
      </Expression>
    </ZExpression>
  </OnUpdate>
  <OnRender>
    <UseMaterial Material="NodeMaterial"/>
    <Repeat Name="NodeRepeat" Count="3" WhileExp="//">
      <OnIteration>
        <ZExpression>
          <Expression>
<![CDATA[// Render light "representation" nodes for demonstation purposes

switch(NodeRepeat.Iteration)
{
  case 0:
    NodeColor.Color = RedLight.Color;
    NodeTransform.Translate = RedLight.Position;
    break;

  case 1:
    NodeColor.Color = GreenLight.Color;
    NodeTransform.Translate = GreenLight.Position;
    break;

  case 2:
    NodeColor.Color = BlueLight.Color;
    NodeTransform.Translate = BlueLight.Position;
    break;
}]]>
          </Expression>
        </ZExpression>
        <RenderSetColor Name="NodeColor" Color="0 0 1 1"/>
        <RenderTransformGroup Name="NodeTransform">
          <Children>
            <RenderMesh Mesh="NodeMesh"/>
          </Children>
        </RenderTransformGroup>
      </OnIteration>
    </Repeat>
  </OnRender>
  <Lights>
    <Light Name="RedLight" Color="1 0 0 1" Kind="1"/>
    <Light Name="GreenLight" Color="0 1 0 1" Kind="1"/>
    <Light Name="BlueLight" Color="0 0 1 1" Kind="1"/>
  </Lights>
  <Content>
    <Model Name="Box" RotationVelocity="0.1 0.2 0">
      <OnRender>
        <UseMaterial Material="BoxMaterial"/>
        <RenderMesh Mesh="BoxMesh"/>
      </OnRender>
    </Model>
    <Mesh Name="BoxMesh">
      <Producers>
        <MeshBox/>
      </Producers>
    </Mesh>
    <Material Name="BoxMaterial"/>
    <Mesh Name="NodeMesh">
      <Producers>
        <MeshSphere Scale="0.25 0.25 0.25" ZSamples="3" RadialSamples="4"/>
      </Producers>
    </Mesh>
    <Material Name="NodeMaterial" Shading="2" Light="0"/>
  </Content>
</ZApplication>
K
ab2
Posts: 6
Joined: Tue Jan 25, 2022 1:39 pm

Re: How to use the ZGE-Light component?

Post by ab2 »

Thank you for your vivid demonstration.

So lights by itself are invisible objects and
the in the example attached nodes can be used
to visualize them.

Can a spot-light effect like in a theatre
with a sharp radial illumnination on an
object be achived?

Or do you know of a good demonstration / page
what light type (spot, point, directional) to use
for what effect on a scene or object and how it should look like?

Many thanks

A
User avatar
Kjell
Posts: 1876
Joined: Sat Feb 23, 2008 11:15 pm

Re: How to use the ZGE-Light component?

Post by Kjell »

Hi Andreas,
ab2 wrote: Fri Feb 18, 2022 11:34 amSo lights by itself are invisible objects and the in the example attached nodes can be used to visualize them.
Yea, i just added the "nodes" so it's easier to understand what's going on.
ab2 wrote: Fri Feb 18, 2022 11:34 amCan a spot-light effect like in a theatre with a sharp radial illumnination on an object be achived?
Yes, but you probably want to use shaders for that. When you use the fixed-function pipeline light is calculated at vertex level, so you'd need high-poly meshes for the effect to look good. Here's a simple example of that using a single spotlight. You can control the "softness" of the spotlight by moving your mouse up/down, and you can toggle the shading style of the scene by pressing 1/2/3/4 on your keyboard ( for debugging purposes ).

Code: Select all

<?xml version="1.0" encoding="iso-8859-1" ?>
<ZApplication Name="App" Caption="ZGameEditor application" AmbientLightColor="0 0 0 1" CameraPosition="0 10 10" CameraRotation="0.125 0 0" MouseVisible="255" FileVersion="2">
  <OnUpdate>
    <ZExpression>
      <Expression>
<![CDATA[// Control spot "softness"

SpotLight.SpotExponent = (1-App.MousePosition.Y)*22.5;

// Animate spot light

float a = sin(App.Time*2)/4;

SpotLight.SpotDirection.X =  sin(a);
SpotLight.SpotDirection.Y = -cos(a);

SpotLight.Position.Y = 8+sin(App.Time/3)*4;]]>
      </Expression>
    </ZExpression>
    <KeyPress Name="ShadingKey" Keys="1234">
      <OnPressed>
        <ZExpression>
          <Expression>
<![CDATA[// Switch scene shading

SceneMaterial.Shading = ShadingKey.KeyIndex;]]>
          </Expression>
        </ZExpression>
      </OnPressed>
    </KeyPress>
  </OnUpdate>
  <OnRender>
    <UseMaterial Material="SceneMaterial"/>
    <RenderMesh Mesh="SceneMesh"/>
  </OnRender>
  <Lights>
    <Light Name="SpotLight" Color="1 1 1 1" Kind="2" SpotDirection="0 0 0" SpotCutoff="22.5"/>
  </Lights>
  <Content>
    <Mesh Name="SceneMesh">
      <Producers>
        <MeshBox Scale="4 4 1" XCount="15" YCount="15" Grid2DOnly="255"/>
        <MeshTransform Position="0 -1 0" Rotation="-0.25 0 0"/>
        <MeshBox XCount="3" YCount="3"/>
        <MeshCombine/>
      </Producers>
    </Mesh>
    <Material Name="SceneMaterial"/>
  </Content>
</ZApplication>
K
ab2
Posts: 6
Joined: Tue Jan 25, 2022 1:39 pm

Re: How to use the ZGE-Light component?

Post by ab2 »

Thanks. That is the tutorial style i really like an can handle
pretty good.

Sorry that I experiment with it .. probably with to few understanding ..
but why in this project gets the Light Color overwritten by the
Scene-Material Color?
User avatar
Kjell
Posts: 1876
Joined: Sat Feb 23, 2008 11:15 pm

Re: How to use the ZGE-Light component?

Post by Kjell »

Hi Andreas,
ab2 wrote: Fri Feb 18, 2022 5:02 pmSorry that I experiment with it .. probably with to few understanding .. but why in this project gets the Light Color overwritten by the Scene-Material Color?
It doesn't. When you for example change SceneMaterial.Color from white into yellow the scene ( box & floor ) appears yellow because at that point it's a yellow box & floor lit by a white light. But if you then for example change the SpotLight.Color from white into red, the yellow box & floor appears red.

The result is always a combination of the object's color and the color of the emitted light.

K
ab2
Posts: 6
Joined: Tue Jan 25, 2022 1:39 pm

Re: How to use the ZGE-Light component?

Post by ab2 »

Sorry without additional tries i choose first yellow for the spotlight and then
orange for the scene. That was a bad Example.
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