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Picking Intersection Vertices


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#1 VoidAccess   Members   -  Reputation: 109

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Posted 27 March 2013 - 09:44 PM

I am trying to grab the closest vertex to my mouse click using picking. I understand that the &t represents distance, but how can I get the distance of each vertex from the mouse click after converting it all to the correct worlds I am able to select the faces of the mesh, but am struggling on selecting the closest vertex.

 

        UINT hitCount;
	float u,v,t;
	ID3D10Blob* allHits;
	d3dxmesh->Intersect(&rayOrigin, &rayDir, &hitCount, 
		&PickedTriangle, &u, &v, &t, &allHits);

I know the vertex is going to be vertex[indices[PickedTriangle*3+0]] ..etc. So how can I get the distance from the click for each vertex in the triangle selected.


Edited by VoidAccess, 27 March 2013 - 09:46 PM.


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#2 JohnnyCode   Members   -  Reputation: 226

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Posted 27 March 2013 - 10:58 PM

you should not get just the triangle, but also the point in the triangle. From there, just inspect the verticies of the triangle and find the closest of the triple.



#3 VoidAccess   Members   -  Reputation: 109

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Posted 28 March 2013 - 05:49 PM

Still having issues getting this to work, I tried to get the shortest distance from the mouse click but its not working right. Just want the closest vertex to be selected from click on the triangle

 

void PickingApp::pick(int sx, int sy)
{
	D3DXMATRIX P = GetCamera().proj();

	// Compute picking ray in view space.
	float vx = (+2.0f*sx/mClientWidth  - 1.0f)/P(0,0);
	float vy = (-2.0f*sy/mClientHeight + 1.0f)/P(1,1);

	D3DXVECTOR3 rayOrigin(0.0f, 0.0f, 0.0f);
	D3DXVECTOR3 rayDir(vx, vy, 1.0f);

	// Tranform to world space.
	D3DXMATRIX V = GetCamera().view();

	D3DXMATRIX inverseV;
	D3DXMatrixInverse(&inverseV, 0, &V);

	D3DXVec3TransformCoord(&rayOrigin, &rayOrigin, &inverseV);
	D3DXVec3TransformNormal(&rayDir, &rayDir, &inverseV);
	
	// Transform to the mesh's local space.
	D3DXMATRIX inverseW;
	D3DXMatrixInverse(&inverseW, 0, &mBaseWorld);

	D3DXVec3TransformCoord(&rayOrigin, &rayOrigin, &inverseW);
	D3DXVec3TransformNormal(&rayDir, &rayDir, &inverseW);
	
	ID3DX10Mesh* d3dxmesh = mBaseMesh.d3dxMesh();
	
	MouseCoord = rayOrigin;

	UINT hitCount;
	float u,v,t;
	ID3D10Blob* allHits;
	d3dxmesh->Intersect(&rayOrigin, &rayDir, &hitCount, 
		&mPickedTriangle, &u, &v, &t, &allHits);

	ReleaseCOM(allHits);
}
drawScene(){
...
...
DWORD i0 = indices[mPickedTriangle*3+0];
DWORD i1 = indices[mPickedTriangle*3+1];
DWORD i2 = indices[mPickedTriangle*3+2];

HR(ib->Unmap());

// Get the vertices of the picked triangle and copy them into our VB.

MeshVertex* vertices = 0;
HR(vb->Map((void**)&vertices, &size));

D3DXVECTOR3* triVerts = 0;
		
HR(mPickedTriVB->Map(D3D10_MAP_WRITE_DISCARD, 0, (void**)&triVerts));

float v1 = sqrt((pow(vertices[i0].pos.x - MouseCoord.x  ,2) + pow(vertices[i0].pos.y - MouseCoord.y,2) + pow(vertices[i0].pos.z - MouseCoord.z,2)));

float v2 = sqrt((pow(vertices[i1].pos.x - MouseCoord.x  ,2) + pow(vertices[i1].pos.y - MouseCoord.y,2) + pow(vertices[i1].pos.z - MouseCoord.z,2)));

float v3 = sqrt((pow(vertices[i2].pos.x - MouseCoord.x  ,2) + pow(vertices[i2].pos.y - MouseCoord.y,2) + pow(vertices[i2].pos.z - MouseCoord.z,2)));

		if(v1 < v2 && v1 < v3)
			triVerts[0] = vertices[i0].pos;
		if(v2 < v1 && v2 < v3)
			triVerts[0] = vertices[i1].pos;
		if(v3 < v1 && v3 < v2)
			triVerts[0] = vertices[i2].pos;
...}

Edited by VoidAccess, 28 March 2013 - 05:49 PM.


#4 VoidAccess   Members   -  Reputation: 109

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Posted 29 March 2013 - 02:47 PM

Finally figured it out. Was mistaking RayOrgin for point in triangle clicked in its local space, but realized that no matter where I clicked the same spot would be selected. So I used the BaryCentric coordinates u,v to find highest influence, which results in the vertice that is the closest on the face to be selected. **This is from Frank D Luna directX book modified for point selection.

 

void PickingApp::pick(int sx, int sy)
{
	D3DXMATRIX P = GetCamera().proj();
	// Compute picking ray in view space.
	float vx = (+2.0f*sx/mClientWidth  - 1.0f)/P(0,0);
	float vy = (-2.0f*sy/mClientHeight + 1.0f)/P(1,1);

	D3DXVECTOR3 rayOrigin(0.0f, 0.0f, 0.0f);
	D3DXVECTOR3 rayDir(vx, vy, 1.0f);

	// Tranform to world space.
	D3DXMATRIX V = GetCamera().view();

	D3DXMATRIX inverseV;
	D3DXMatrixInverse(&inverseV, 0, &V);

	D3DXVec3TransformCoord(&rayOrigin, &rayOrigin, &inverseV);
	D3DXVec3TransformNormal(&rayDir, &rayDir, &inverseV);

	// Transform to the mesh's local space.
	D3DXMATRIX inverseW;
	D3DXMatrixInverse(&inverseW, 0, &mBaseWorld);

	D3DXVec3TransformCoord(&rayOrigin, &rayOrigin, &inverseW);
	D3DXVec3TransformNormal(&rayDir, &rayDir, &inverseW);
	
	ID3DX10Mesh* d3dxmesh = mBaseMesh.d3dxMesh();
	
	UINT hitCount;
	float u,v,t;
	ID3D10Blob* allHits;
	d3dxmesh->Intersect(&rayOrigin, &rayDir, &hitCount, 
		&mPickedTriangle, &u, &v, &t, &allHits);

	float v0 = 1 - u - v;
	float v1 = u;
	float v2 = v;

	if(v0 > v1 && v0 > v2)
		inf = mPickedTriangle * 3;
	if(v1 > v0 && v1 > v2)
		inf = mPickedTriangle * 3 + 1;
	if(v2 > v0 && v2 > v1)
		inf = mPickedTriangle * 3 + 2;

	ReleaseCOM(allHits);
}
drawScene(){
.....
......
if( mPickedTriangle != -1 )
    {
        ID3DX10Mesh* d3dxmesh = mBaseMesh.d3dxMesh();

        ID3DX10MeshBuffer* vb = 0;
        ID3DX10MeshBuffer* ib = 0;
        HR(d3dxmesh->GetVertexBuffer(0, &vb));
        HR(d3dxmesh->GetIndexBuffer(&ib));

        // Get the indices of the picked triangle.

        DWORD* indices = 0;
        SIZE_T size;
        HR(ib->Map((void**)&indices, &size));
        
        DWORD i0 = indices[inf];
    
        HR(ib->Unmap());

        // Get the vertices of the picked triangle and copy them into our VB.

        MeshVertex* vertices = 0;
        HR(vb->Map((void**)&vertices, &size));

        D3DXVECTOR3* triVerts = 0;
        
        HR(mPickedTriVB->Map(D3D10_MAP_WRITE_DISCARD, 0, (void**)&triVerts));
        
        triVerts[0] = vertices[i0].pos;
        
        mPickedTriVB->Unmap();
        HR(vb->Unmap());

        ReleaseCOM(vb);
        ReleaseCOM(ib);

        // Render the picked triangle specially to distinguish it
        // from the other triangles.

        md3dDevice->IASetInputLayout(InputLayout::Pos);
        md3dDevice->IASetPrimitiveTopology(D3D10_PRIMITIVE_TOPOLOGY_POINTLIST);
        UINT stride = sizeof(D3DXVECTOR3);
        UINT offset = 0;
        md3dDevice->IASetVertexBuffers(0, 1, &mPickedTriVB, &stride, &offset);

        D3D10_TECHNIQUE_DESC techDesc;
        mPickedTech->GetDesc( &techDesc );

        D3DXMATRIX W = mBaseWorld;
        D3DXMATRIX V = GetCamera().view();
        D3DXMATRIX P = GetCamera().proj();

        D3DXMATRIX WVP = W*V*P;

        mfxPickedWVPVar->SetMatrix((float*)&WVP);

        for(UINT i = 0; i < techDesc.Passes; ++i)
        {
            ID3D10EffectPass* pass = mPickedTech->GetPassByIndex(i);
            pass->Apply(0);

            md3dDevice->Draw(1, 0);
        }
    }
}

 

 

.


Edited by VoidAccess, 29 March 2013 - 02:48 PM.





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