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vecLightViewPos question #480006
05/12/20 23:29
05/12/20 23:29
Joined: May 2009
Posts: 5,287
Caucasus
3run Online OP
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3run  Online OP
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Hi!

I would like to know more about vecLightViewPos[8], manual just doesn't say anything about it... I'm trying to get the position of each light via pp shader, and thought, that I need to get position relative to the view coordinates, so that's why I'm trying to learn more about vecLightViewPos. I thought that it's float3 with x, y being the screen coordinates and z the lightrange... but this doesn't work, then I tried to use it as a float4 with .w being the lightrange (as for vecLightPos), but this doesn't work either... What would you guys suggest, what am I doing wrong?

Last edited by 3run; 05/13/20 19:55.

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Re: vecLightViewPos question [Re: 3run] #480008
05/13/20 08:29
05/13/20 08:29
Joined: Jun 2007
Posts: 1,328
Hiporope and its pain
txesmi Offline
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Hi,
'view space' is a Carthesian three dimensional coordinate system like 'world space', but aligned with the position and rotation of a camera. In d3d9, the X axe goes forward on the view direction, Y up, and Z to the left.

worldSpacePos * matView -> viewSpacePos // it had an error, fixed.
viewSpacePos * matViewInv -> worldSpacePos








Last edited by txesmi; 05/13/20 11:58. Reason: ERROR!!!!
Re: vecLightViewPos question [Re: 3run] #480010
05/13/20 10:42
05/13/20 10:42
Joined: May 2009
Posts: 5,287
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3run Online OP
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In this case, I should get lightrange from the vecLightPos.w. As for the position of the light in screen coordinates, vecLightViewPos doesn't help, I guess I need to convert vecLightPos.xyz to screen pos? Already tried oPos = mul(iPos,matWorldViewProj); but that didn't help either.

Edit: I found this algorithm to convert from cartesian to screen:
Code
screenX = cartX + screen_width/2
screenY = screen_height/2 - cartY

// converted it into 
float pos_x = vecLightViewPos[i].x + vecViewPort.x / 2;
float pos_y = vecViewPort.y / 2 - vecLightViewPos[i].y;


It already looks a bit more closer to what I want to archive, but it looks like positions aren't correct when close to the light sources...
[Linked Image]
But on distance it's almost what I want to archive.
[Linked Image]

Last edited by 3run; 05/13/20 10:54.

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Re: vecLightViewPos question [Re: 3run] #480014
05/13/20 12:33
05/13/20 12:33
Joined: Jun 2007
Posts: 1,328
Hiporope and its pain
txesmi Offline
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The only way to get correct screen coordinates is throgh the normalized device coordinate system (NDC) which can be computed by multiplying object space coordinates by matWorldViewProj, or world space coordinates by matViewProj, or view space coordinates by matProj, since the projection of the camera is determinant.

Code
float2 normalizedProjectionCoordinatesXY = mul(float4(vecLightPos[i].xyz, 1.0f), matViewProj).xy; // range: -1 <-> 1
// or, with the same price and same result:
// float2 normalizedProjectionCoordinatesXY = mul(float4(vecLightViewPos[i].xyz, 1.0f), matProj).xy;

float2 screenCoordinates = (0.5f + normalizedProjectionCoordinatesXY * 0.5f) * vecViewport.xy; // range: 0 <-> screen_size - 1


As far as I understand, the radius of the light can't be directly tranformed to screen cordinates as easy as common coordinates. It will need to compute a position in the desired coordinate system, transform it to NDC, compute the resulting radius of the projection and use it with light position screen coordinates to draw the projected circle of the light sphere.

Code
float2 normalizedProjectionCoordinatesXY = mul(float4(vecLightViewPos[i].xyz, 1.0f), matProj).xy;
float normalizedProjectionCoordinatesOfOuterPointOfLightSphereX = mul(float4(vecLightViewPos[i].xy, vecLightViewPos[i].z - vecLightViewPos[i].w, 1.0f), matProj).x ; // doing the same in world space would need far more computations
float projectedLightRadiusInScreenPixels = vecViewPort.x * (normalizedProjectionCoordinatesOfOuterPointOfLightSphereX - normalizedProjectionCoordinatesXY.x) / 2.0f;


Notice that in order to compute the projected light radius, the original light radius is subtracted to the view space Z coordinate of the light, which is the inversed X coordinate in screen space. View space YZ plane is parallel to the camera projection plane, so it is proportional to the distance according to the projection.

Salud!

DISCLAIMER: I did not test any of the code above, I might had failed but I am pretty sure it is correct.

Re: vecLightViewPos question [Re: 3run] #480016
05/13/20 13:36
05/13/20 13:36
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I tried out the following:
Code
float2 normalizedProjectionCoordinatesXY = mul(float4(vecLightViewPos[i].xyz, 1.0f), matProj).xy;
float normalizedProjectionCoordinatesOfOuterPointOfLightSphereX = mul(float4(vecLightViewPos[i].xy, vecLightViewPos[i].z - vecLightViewPos[i].w, 1.0f), matProj).x;
float projectedLightRadiusInScreenPixels = vecViewPort.x * (normalizedProjectionCoordinatesOfOuterPointOfLightSphereX - normalizedProjectionCoordinatesXY.x) / 2.0f;
float2 screenCoordinates = (0.5f + normalizedProjectionCoordinatesXY * 0.5f) * vecViewPort.xy;
So I set position to screenCoordinates.xy and range to projectedLightRadiusInScreenPixels, but screen is plain dark grin
Tried out matWorldViewProj and matViewProj instead of matProj, but no changes... Also, does vecLightViewPos[i].w contain lightrange?

Edit: this is what I want to archive at the end
[Linked Image]

Last edited by 3run; 05/13/20 15:34.

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Re: vecLightViewPos question [Re: 3run] #480017
05/13/20 16:04
05/13/20 16:04
Joined: Feb 2013
Posts: 122
Maysville, Ga
Evo Offline
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I wish I could help, but I don't have enough knowledge of shaders to be of assistance. I've also been trying to achieve a similar result with pure 2d and panels, (without 3d). My original concept was to apply a shader to a single black panel that is the same size as the 2d level. Then somehow cut out a feathered circle around the player as well as around all light panels that are placed in the 2d level. But I've recently had no luck in getting it to work correctly.

Re: vecLightViewPos question [Re: 3run] #480018
05/13/20 16:21
05/13/20 16:21
Joined: May 2009
Posts: 5,287
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3run Online OP
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Thank you for reply Evo! Unfortunately, I'm also not having enough knowledge to be able to get such simple stuff working... :<
If only I could, I would be happy to get this or those shadow shaders I've converted from shadertoy working with acknex and 3d/2d scenes.


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Re: vecLightViewPos question [Re: 3run] #480020
05/13/20 16:44
05/13/20 16:44
Joined: Jun 2007
Posts: 1,328
Hiporope and its pain
txesmi Offline
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mm, I am sorry, I commited three faults.

1. The normalized device coordinates are computed by dividing the result of the multiply by matProj (or so) by its w component. The raw result of the multiply is known to be in 'clip space'.
2. The y component of the result must be inversed in order to get {0, 0} at the top left corner of the screen.
3. Surprisingly, normalized device coordinates need to be divided by 4 to be in a 0<->1 range. This broke my knowledge, it has always been in a -1<->1 range... shocked

Code
float4 clipSpaceCoordinates = mul(float4(vecLightPos[i].xyz, 1.0f), matViewProj);
float2 normalizedProjectionCoordinatesXY = clipSpaceCoordinates.xy / clipSpaceCoordinates.w;
float2 normalizedScreenCoordinates;
normalizedScreenCoordinates.x = (1.0f + normalizedProjectionCoordinatesXY.x) / 4.0f;
normalizedScreenCoordinates.y = (1.0f - normalizedProjectionCoordinatesXY.y) / 4.0f;
float2 screenCoordinates = normalizedScreenCoordinates * vecViewPort.xy;


A PP effect needs the CHILD flag so it inherits the transformation matrices and light list from the previous stage.

Here goes an example that computes the normalized screen coordinates of a rendered entity:

Code
#include <acknex.h>
#include <default.c>

MATERIAL *mtlNormalizedScreenCoords =
{
	effect = "
		float4x4 matWorldViewProj;
	
		void VS (
			in  float4 inPos     : POSITION,
			out float4 outPos    : POSITION,
			out float4 outColor0 : COLOR0)
		{
			outPos = mul(inPos, matWorldViewProj);
			outColor0.r = (1.0f + outPos.x / outPos.w) / 4.0f;
			outColor0.g = (1.0f - outPos.y / outPos.w) / 4.0f;
			outColor0.b = 0.0;
			outColor0.a = 1.0;
		}
	
		technique
		{
			pass
			{
				VertexShader = compile vs_2_0 VS();
			}
		}
	";
}

void main()
{
	wait(1);
	level_load(SPHERE_MDL);
	camera->material = mtlNormalizedScreenCoords;
	camera->x = -30;
	
	while(!key_esc)
	{
		if(proc_status(def_move) == 0)
		{
			camera->pan = clamp(camera->pan + mickey.x * 0.2, -30, 30);
			camera->tilt = clamp(camera->tilt + mickey.y * 0.2, -20, 20);
		}
		wait(1);
	}
	
	sys_exit(NULL);
}



Last edited by txesmi; 05/13/20 18:30. Reason: error fix
Re: vecLightViewPos question [Re: 3run] #480021
05/13/20 18:21
05/13/20 18:21
Joined: May 2009
Posts: 5,287
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3run Online OP
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3run  Online OP
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Thank you for examples, txesmi! I have a question.
Code
float3 clipSpaceCoordinates = mul(float4(vecLightPos[i].xyz, 1.0f), matViewProj).xy;
float2 normalizedProjectionCoordinatesXY = clipSpaceCoordinates.xy / clipSpaceCoordinates.w;
clipSpaceCoordinates is a float3, but you use it's clipSpaceCoordinates .w in normalizedProjectionCoordinatesXY calculation.
Also, in clipSpaceCoordinates itself you only set .xy while calculating it.
So in order to compile, I've changed float3 clipSpaceCoordinates to float4, but it doesn't work.
Also, I've set CHILD flag for the pp view.

EDIT:
Also in
Code
normalizedScreenCoordinates.y = (1.0f - normalizedProjectionCoordinatesXY.y) / 4.0f;
You used
Code
normalizedProjectionCoordinatesXY.x
Instead of Y is that intentional?

EDIT2: ok, I see that you fixed the previous post, but it still doesn't work for some reason...
This is the code I tried out (tried both vecLightViewPos and vecLightPos).
Code
float4 clipSpaceCoordinates = mul(float4(vecLightViewPos[i].xyz, 1.0f), matViewProj);
float2 normalizedProjectionCoordinatesXY = clipSpaceCoordinates.xy / clipSpaceCoordinates.w;
float2 normalizedScreenCoordinates;
normalizedScreenCoordinates.x = (1.0f + normalizedProjectionCoordinatesXY.x) / 4.0f;
normalizedScreenCoordinates.y = (1.0f - normalizedProjectionCoordinatesXY.y) / 4.0f;
float2 screenCoordinates = normalizedScreenCoordinates * vecViewPort.xy;

float normalizedProjectionCoordinatesOfOuterPointOfLightSphereX = mul(float4(vecLightViewPos[i].xy, vecLightViewPos[i].z - vecLightViewPos[i].w, 1.0f), matProj).x;
float projectedLightRadiusInScreenPixels = vecViewPort.x * (normalizedProjectionCoordinatesOfOuterPointOfLightSphereX - normalizedProjectionCoordinatesXY.x) / 2.0f;

Last edited by 3run; 05/13/20 19:55.

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Re: vecLightViewPos question [Re: 3run] #480022
05/13/20 18:42
05/13/20 18:42
Joined: Jun 2007
Posts: 1,328
Hiporope and its pain
txesmi Offline
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No, sorry, you are right. Both things should be as you say. float4 clip coors and y component. I am pretty absent-minded today. I wanted to give you an answer before get out of home and the hurry defeated me in the original examples code modification. Excuse the inconvenience.

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