if i have a vertex array,and a normal array ,how to render 3DObject without conversion?

[jimfar]

i just know now rendering a object into QT3D engine must be like this ,"one vertext and one normal,
one vertext and one normal,one vertext and one normal......"but i wanna the datastruct is like this "a A set of vertices and A set of noramls" ,and the count of vertices is equal to noramls, how to render this mesh ? who could help me

[jimfar]

        int nVerts =2946;
        QByteArray vertexBufferData;
		QByteArray normalBufferData;
        auto vertexDataBuffer = new Qt3DRender::QBuffer(Qt3DRender::QBuffer::VertexBuffer, customGeometry);
		auto normalDataBuffer = new Qt3DRender::QBuffer(Qt3DRender::QBuffer::VertexBuffer, customGeometry);

		/////vertexs is a array of vertex
		/////pnormals is a array of normal 
 	    vertexBufferData = vertexBufferData.setRawData((char*)vertexs, nVerts * sizeof(float[3])); 	
		normalBufferData = normalBufferData.setRawData((char*)pnormals, nVerts * sizeof(float[3])); 
		 vertexBufferData += normalBufferData;
		vertexDataBuffer->setData(vertexBufferData);


       const quint32 stride = (0 + 1) * sizeof(float[3]);
		auto positionAttribute = new Qt3DRender::QAttribute();
		positionAttribute->setAttributeType(Qt3DRender::QAttribute::VertexAttribute);
		positionAttribute->setBuffer(vertexDataBuffer);
		positionAttribute->setDataType(Qt3DRender::QAttribute::Float);
		positionAttribute->setDataSize( 3);//xyz
		positionAttribute->setVertexSize(3);
		positionAttribute->setByteOffset(0);
		positionAttribute->setByteStride(stride);
		positionAttribute->setCount(nVerts);
		positionAttribute->setName(Qt3DRender::QAttribute::defaultPositionAttributeName());


		auto normalAttribute = new Qt3DRender::QAttribute();
		normalAttribute->setAttributeType(Qt3DRender::QAttribute::VertexAttribute);
		normalAttribute->setBuffer(vertexDataBuffer);
		normalAttribute->setDataType(Qt3DRender::QAttribute::Float);
		normalAttribute->setDataSize(3);//xyz
		normalAttribute->setByteOffset(nVerts * sizeof(float[3]));
		normalAttribute->setByteStride(stride);
		normalAttribute->setCount(nVerts);
		normalAttribute->setName(Qt3DRender::QAttribute::defaultNormalAttributeName());

        auto customMeshRenderer = new Qt3DRender::QGeometryRenderer;
		auto customGeometry = new Qt3DRender::QGeometry(customMeshRenderer);
		customGeometry->addAttribute(positionAttribute);
		customMeshRenderer->setPrimitiveType(Qt3DRender::QGeometryRenderer::Triangles);
		customMeshRenderer->setGeometry(customGeometry);
		customMeshRenderer->setVertexCount(nVerts);

this is code snippet,why it cant render ?

[jimfar]

ByteStride is right and ByteOffset is also right (nVerts * sizeof(float[3])) why it dosent work

[jimfar]

maybe i dont grasp the true meaning of these api ,who could give me some advice ..

[jimfar]

glDrawArrays (GLenum mode, GLint first, GLsizei count); does QT3D have the similar api or apis to implementate the similar function

[jimfar]

ok i found a way to fixed this problem by using geometry shader to calculate the normal,and then i can just need vertex and index to render my object .more detail about using geometry shader to calculate the normal, please see QT3D example "wireframe.pro"