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# [D3D]A problem about pick sequence!

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### #1kgs  Members   -  Reputation: 205

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Posted 12 August 2012 - 06:49 AM

I followed Frank Luna's book :Introducting to 3D game programing :A shader approach
And write a program.
The problem is that when the picking ray go through multi object,it may hit a object far from the camera first,but not the near one!
this is my code:
static bool clickOnce = true;
static bool clickAgain = true;
D3DXVECTOR3 originW(0.0f, 0.0f, 0.0f);
D3DXVECTOR3 dirW(0.0f, 0.0f, 0.0f);
if( gDInput->mouseButtonDown(0) )
{
if(clickAgain == clickOnce)
{
clickAgain = clickOnce;
clickOnce = false;
getWorldPickingRay(originW, dirW);
}
}
else
{
clickOnce = true;
}

for(int x = 0; x < 32; x++)
{
for(int y = 0; y < 32; y++)
{
for(int z = 0; z < 32; z++)
{
//x,y,z means objects position and there are all box
if(mMapClass->GetPosID(x, y, z))//check texture ID
{
D3DXMATRIX T;
D3DXMatrixTranslation(&T, x, y, z);
D3DXMATRIX toWorld = T;
AABB box;
mChunkBox.xform(toWorld, box);

if(D3DXBoxBoundProbe(&box.minPt, &box.maxPt, &originW, &dirW) )
{
//destroy the box
}
//and then draw object in position (x, y, z)
}
}
}
}

void getWorldPickingRay(D3DXVECTOR3& originW, D3DXVECTOR3& dirW)
{
POINT s;
GetCursorPos(&s);
ScreenToClient(mhMainWnd, &s);
float w = (float)md3dPP.BackBufferWidth;
float h = (float)md3dPP.BackBufferHeight;
D3DXMATRIX proj = gCamera->proj();
float x = (2.0f*s.x/w - 1.0f) / proj(0,0);
float y = (-2.0f*s.y/h + 1.0f) / proj(1,1);
D3DXVECTOR3 origin(0.0f, 0.0f, 0.0f);
D3DXVECTOR3 dir(x, y, 1.0f);
D3DXMATRIX invView;
D3DXMatrixInverse(&invView, 0, &gCamera->view());
D3DXVec3TransformCoord(&originW, &origin, &invView);
D3DXVec3TransformNormal(&dirW, &dir, &invView);
D3DXVec3Normalize(&dirW, &dirW);
}

Is there any problems in my code?

And sorry for my poor english

Edited by kgs, 12 August 2012 - 07:01 AM.

My english is very poor!

### #2PhillipHamlyn  Members   -  Reputation: 499

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Posted 12 August 2012 - 07:49 AM

I seem to remember D3D providing a function for this, using mesh objects, which returned all intercepted meshes sorted into distance order. This seems to suggest to me that you will expect to find objects yourself in any order which you then need to sort by distance in order to find the nearest one. Because the world is not sorted by distance-from-viewer and ray you cast will find objects in whatever order they are stored in.

### #3kgs  Members   -  Reputation: 205

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Posted 12 August 2012 - 09:05 AM

I seem to remember D3D providing a function for this, using mesh objects, which returned all intercepted meshes sorted into distance order. This seems to suggest to me that you will expect to find objects yourself in any order which you then need to sort by distance in order to find the nearest one. Because the world is not sorted by distance-from-viewer and ray you cast will find objects in whatever order they are stored in.

HRESULT D3DXIntersect(
__in LPD3DXBASEMESH pMesh,
__in const D3DXVECTOR3 *pRayPos,
__in const D3DXVECTOR3 *pRayDir,
__out BOOL *pHit,
__out DWORD *pFaceIndex,
__out FLOAT *pU,
__out FLOAT *pV,
__out FLOAT *pDist,
__out LPD3DXBUFFER *ppAllHits,
__out DWORD *pCountOfHits
);
so is the pDist return the shortest distance?
But I still don't known how to do with this shortest distance.
My english is very poor!

### #4kgs  Members   -  Reputation: 205

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Posted 12 August 2012 - 11:35 AM

Now I have changed my code to triangle Pick using D3DXIntersect
But it still get multi result, I only want a closest one to pick, please help me

Edited by kgs, 12 August 2012 - 11:36 AM.

My english is very poor!

### #5majorbrot  Members   -  Reputation: 847

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Posted 12 August 2012 - 01:19 PM

what about putting all intersecting meshes in a vector with a pointer to the mesh or some other identifier plus the distance? than you can iterate through the vector and save the shortest distance with the identifier.

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