Skybox spherical projection on surfaces

Help & Support
1

Good afternoon everyone,

Is there any way to do a Spherical projection of an skybox on other objects?
Let me explain:

step1
step1.jpg1000×730 35.4 KB

I have a model of a room and a sphere skybox with a realistic image of this room. Now i need to project the skybox texture/image on the room like the image blow shows.
step2
step2.jpg1000×730 86.1 KB

Someone has an idea of how to do this?

2

I did that for screen mapping (exactly like on the second image)

Do you want me to share this code or meaningless?

3

Please share. I was trying to do the camera as well as you might have noticed from my old posts, but I just realized that I would need the spherical projection and I got discouraged, but it will be of great help to see your running.

4

Okay.

So, In a nutshell, you have to calculate screen-space coords for each vertex in Vertex Shader.


varying vec2 vVertex_screenCoords; 

uniform mat4 matrix_projection;

vec2 getScreenCoords(vec3 position) {
    vec4 world_position = matrix_model * vec4(position, 1.0);
    vec4 view_position = matrix_viewProjection * world_position;    
    return vec2((view_position.x + 10.0 ) / 20.0 , (view_position.y + 10.5) / 20.0);
}

I have to say that this function isn’t correct. I don’t know why and how to fix it.
Probably you’re more lucky and somebody would help you.

Then, bypass it to Fragment one and texel from texture by these coords.

I did that via shader chunk system, so

image

In my case there is also a power param, but you don’t need that. So either texel right from texture or replace shader’s chunk just like me, if you need shadows and etc.

5

Thanks, i’ll try this, but i need to learn about shaders first kkkk

6

I’m breaking my head here to understand these shaders. 1 question, how do you pass to the shader that ‘varying vec2 vVertex_screenCoords’? You calculate first via javascript and then how do you pass each vertex information to vertex shader?

7

Nope, screen position is the same for whole draw call.
So just by setting additional parameter, just like in a tutorial.