C++ TType::getMatrixRows方法代码示例

// Recursively figure out how many bytes of xfb buffer are used by the given type.
// Return the size of type, in bytes.
// Sets containsDouble to true if the type contains a double.
// N.B. Caller must set containsDouble to false before calling.
unsigned int TIntermediate::computeTypeXfbSize(const TType& type, bool& containsDouble) const
{
    // "...if applied to an aggregate containing a double, the offset must also be a multiple of 8, 
    // and the space taken in the buffer will be a multiple of 8.
    // ...within the qualified entity, subsequent components are each 
    // assigned, in order, to the next available offset aligned to a multiple of
    // that component's size.  Aggregate types are flattened down to the component
    // level to get this sequence of components."

    if (type.isArray()) {        
        // TODO: perf: this can be flattened by using getCumulativeArraySize(), and a deref that discards all arrayness
        assert(type.isExplicitlySizedArray());
        TType elementType(type, 0);
        return type.getOuterArraySize() * computeTypeXfbSize(elementType, containsDouble);
    }

    if (type.isStruct()) {
        unsigned int size = 0;
        bool structContainsDouble = false;
        for (int member = 0; member < (int)type.getStruct()->size(); ++member) {
            TType memberType(type, member);
            // "... if applied to 
            // an aggregate containing a double, the offset must also be a multiple of 8, 
            // and the space taken in the buffer will be a multiple of 8."
            bool memberContainsDouble = false;
            int memberSize = computeTypeXfbSize(memberType, memberContainsDouble);
            if (memberContainsDouble) {
                structContainsDouble = true;
                RoundToPow2(size, 8);
            }
            size += memberSize;
        }

        if (structContainsDouble) {
            containsDouble = true;
            RoundToPow2(size, 8);
        }
        return size;
    }

    int numComponents;
    if (type.isScalar())
        numComponents = 1;
    else if (type.isVector())
        numComponents = type.getVectorSize();
    else if (type.isMatrix())
        numComponents = type.getMatrixCols() * type.getMatrixRows();
    else {
        assert(0);
        numComponents = 1;
    }

    if (type.getBasicType() == EbtDouble) {
        containsDouble = true;
        return 8 * numComponents;
    } else
        return 4 * numComponents;
}

//.........这里部分代码省略.........
    //
    //   8. If the member is an array of S row-major matrices with C columns and R
    //      rows, the matrix is stored identically to a row of S  R row vectors with C
    //      components each, according to rule (4).
    //
    //   9. If the member is a structure, the base alignment of the structure is N , where
    //      N is the largest base alignment value of any    of its members, and rounded
    //      up to the base alignment of a vec4. The individual members of this substructure 
    //      are then assigned offsets by applying this set of rules recursively,
    //      where the base offset of the first member of the sub-structure is equal to the
    //      aligned offset of the structure. The structure may have padding at the end;
    //      the base offset of the member following the sub-structure is rounded up to
    //      the next multiple of the base alignment of the structure.
    //
    //   10. If the member is an array of S structures, the S elements of the array are laid
    //       out in order, according to rule (9).
    //
    //   Assuming, for rule 10:  The stride is the same as the size of an element.

    stride = 0;
    int dummyStride;

    // rules 4, 6, 8, and 10
    if (type.isArray()) {
        // TODO: perf: this might be flattened by using getCumulativeArraySize(), and a deref that discards all arrayness
        TType derefType(type, 0);
        alignment = getBaseAlignment(derefType, size, dummyStride, std140, rowMajor);
        if (std140)
            alignment = std::max(baseAlignmentVec4Std140, alignment);
        RoundToPow2(size, alignment);
        stride = size;  // uses full matrix size for stride of an array of matrices (not quite what rule 6/8, but what's expected)
                        // uses the assumption for rule 10 in the comment above
        size = stride * type.getOuterArraySize();
        return alignment;
    }

    // rule 9
    if (type.getBasicType() == EbtStruct) {
        const TTypeList& memberList = *type.getStruct();

        size = 0;
        int maxAlignment = std140 ? baseAlignmentVec4Std140 : 0;
        for (size_t m = 0; m < memberList.size(); ++m) {
            int memberSize;
            // modify just the children's view of matrix layout, if there is one for this member
            TLayoutMatrix subMatrixLayout = memberList[m].type->getQualifier().layoutMatrix;
            int memberAlignment = getBaseAlignment(*memberList[m].type, memberSize, dummyStride, std140,
                                                   (subMatrixLayout != ElmNone) ? (subMatrixLayout == ElmRowMajor) : rowMajor);
            maxAlignment = std::max(maxAlignment, memberAlignment);
            RoundToPow2(size, memberAlignment);         
            size += memberSize;
        }

        // The structure may have padding at the end; the base offset of
        // the member following the sub-structure is rounded up to the next
        // multiple of the base alignment of the structure.
        RoundToPow2(size, maxAlignment);

        return maxAlignment;
    }

    // rule 1
    if (type.isScalar())
        return getBaseAlignmentScalar(type, size);

    // rules 2 and 3
    if (type.isVector()) {
        int scalarAlign = getBaseAlignmentScalar(type, size);
        switch (type.getVectorSize()) {
        case 2:
            size *= 2;
            return 2 * scalarAlign;
        default: 
            size *= type.getVectorSize();
            return 4 * scalarAlign;
        }
    }

    // rules 5 and 7
    if (type.isMatrix()) {
        // rule 5: deref to row, not to column, meaning the size of vector is num columns instead of num rows
        TType derefType(type, 0, rowMajor);
            
        alignment = getBaseAlignment(derefType, size, dummyStride, std140, rowMajor);
        if (std140)
            alignment = std::max(baseAlignmentVec4Std140, alignment);
        RoundToPow2(size, alignment);
        stride = size;  // use intra-matrix stride for stride of a just a matrix
        if (rowMajor)
            size = stride * type.getMatrixRows();
        else
            size = stride * type.getMatrixCols();

        return alignment;
    }

    assert(0);  // all cases should be covered above
    size = baseAlignmentVec4Std140;
    return baseAlignmentVec4Std140;
}